I've been spying on my sister for about two months; watching her change her clothes through her bedroom window. I never thought I'd take it any farther than just spying. She is my sister, after all. To me it's just a good way to see some tits, ass and pussy on a regular basis.

My sister and I are twins. We get along great, not like some brothers and sisters. Our dad is in the Navy and we've never lived anywhere long enough to develop close friendships with other kids, so we've become each other's best friend by default. We're both pretty smart and have tested in the top percentile of our classes academically. We do just about everything together. We go to the movies, hang out at the mall, sometimes we even double date. I also think we have a special connection because we're twins.

During our senior year in high school, right after we turned 18, we moved to San Diego and our dad shipped out for a six-month tour of duty aboard a destroyer. Mom works as a paralegal, for a law firm downtown, so we are home by ourselves after school every day. This is our first house with a pool and that's where my sister and I spend most of our time.

I've noticed my sister's body developing over the last couple of years, but I was not prepared for the feast my eyes got when my sexy, twin sister started spending most of her time in a skimpy swimsuit. She's blossomed into a size 34B and the sexy curves of her tits, visible around the minimal material of her swimsuit top, captivate me. Her firm, young ass rounds out the bottoms of her swimsuit in a way that would make any guy look twice. Being around my sister, in our swimsuits every day, is getting to me. I find that I can't keep my eyes, or my mind, off of her firm, young tits or her cute little ass.

We are playing in our backyard pool one afternoon, dunking each other and generally fooling around, when my sister climbs her way up my body and tries to dunk me. She seems oblivious to the amount of bare skin contact between us, but my cock certainly isn't. I have to maneuver myself sideways so she won't feel my hard-on.

Her swimsuit top is stretched tightly across her breasts and, when it gets wet, her nipples make pretty obvious bumps in the thin material. Pushing on my shoulders, she lifts herself out of the water, trying to dunk me. At 18 I've had a few girlfriends, but I've never seen a sight as sexy as my sister's tanned tits two inches from my face. I desperately want to see them uncovered.

We finish in the pool and my sister goes in the house to change. My cock hardens as I watch her tight ass wiggle across the patio toward the sliding glass door. I can't believe how badly I want to see her naked body. I tell her I'm going to check the filtration system and will be right in.

Instead, I walk around the side of the house to my sister's bedroom window. This side of our house has a covered walkway with lots of bushes. I position myself to see in her window, without her or our nosy neighbors seeing me. I look for an opening in her blinds so I can watch her change, but the way the blinds are positioned, I can only see the ceiling. I give up (for that day) and go in to change.

The next day while my sister is watching TV in the family room, I sneak into her room and adjust her blinds, leaving about an inch and a half gap between the bottom of the blind and the windowsill. After changing into my swimsuit, I head out toward the pool.

"Hey Lisa, I'm going in the pool. Want to go?" I ask my sister casually as I walk through the family room and out the sliding glass door.

"Sure, I'll be there in a sec," she says, getting up from the couch and turning off the TV.

That's my cue. Around the house I go. I get to her window just in time to see her entering her bedroom. She is pulling her shirt up as she closes the door. I stand there mesmerized, as she tosses the shirt on her bed and begins taking off her bra. My cock jumps, creating a bulge in my swimsuit, when I get my first look at her teen sized mounds. I stare at them, enraptured by her inch and a half areolas and little pink nipples. But the real treat is watching her unzip her shorts and slide them down her tan legs.

My sister is average height, with a flat stomach, and a body that curves in all the right places. She turns from the window while taking her shorts off and I'm looking at her panty-clad ass, as she bends over. I start rubbing my cock through my swimsuit, to relieve some of the pressure, as she hooks her thumbs in the waistband of her panties and slides them down.

My god! Her ass is spectacular. Her firm, young cheeks curve just enough to make you want to grab a handful and plant kisses all over them. Bent over like that, a few blonde pubic hairs and just a hint of her pussy lips are visible between her legs. I can't wait for her to turn around so I can see the rest of her. But, instead, as I'm admiring her ass, she slips her swimsuit bottom over her feet and pulls it up. I get one last peek at her ass, before she grabs the elastic on the sides of her suit and pulls them down to cover her cute round cheeks. Hooking her swimsuit top, she turns it around so the hook is in the back and the cups are in the front.

I belatedly notice that she's standing in front of her dresser, which has a big mirror over it. Through the mirror, I get one more look at her nipple-tipped mounds as she slips her arms in the straps, pulls her swim suit top up over her chest, and reaches inside each cup to adjust her tits. She checks herself in the mirror and opens her bedroom door.

Shit! I better get in the pool fast. I've been so engrossed in watching her change that I didn't think about what would happen if she saw me coming around the side of the house and I wasn't even wet yet. Speaking of cumming around the side of the house; that was going to have to wait. I'm still hard as I hit the pool at a run and swim to the deep end, treading water, as she comes out of the house.

"How's the water?"

"Great, come on in!" I yell, hoping the cool water will relieve me of my uncomfortable, and obvious condition.

We stay in the pool for about an hour, fooling around like we usually do. If my sister notices anything different, in the way I'm acting or looking at her, she doesn't let on. I'm trying to act normal, but every time her tits get close to me, I can't help but think about her pink nipples sticking out from her firm young breasts. When she sits on the edge of the pool, dangling her legs and pushing the water sideways with her foot, I stare at the crotch of her swimsuit, imagining how her pussy looks. Fortunately, I don't have to imagine for very long.

When we're finished, I again make an excuse about checking the filter and run around to the side of the house. I wait a while and start getting nervous that maybe my sister is coming back outside. I'm just about to abandon my position when she walks into her bedroom with a towel wrapped around her. She's taken her wet swimsuit off in the bathroom and is now dropping the towel, as she closes her bedroom door. My eyes are glued to her pussy and what a sight! It isn't the first pussy I've ever seen, but the excitement of seeing my twin sister's pussy, makes my cock spring to life.

She has a nice v-shaped patch of blonde hair that almost covers her pussy lips, which are protruding slightly downward between her legs. I'm rubbing my cock like crazy and trying to take it all in, remembering how fast she changed earlier. But I'm in for a wonderful surprise. My sister puts on lotion after she swims - before she gets dressed.

I watch her standing naked, in front of the mirror, squeezing lotion onto her hands. She rubs her hands together and starts massaging lotion onto her arms and shoulders. I love the way her firm tits move, pointing her pink nipples right at the mirror, when she reaches up to rub lotion on her shoulders. Pulling my hard cock out of my swimsuit, I begin seriously stroking it, as she rubs lotion across her stomach.

Beginning just below her navel, she rubs the lotion up over her flat stomach and her ribs. Lifting each breast, one at a time, she gently squeezes it, as she rubs the lotion in. It looks like she lingers a little on her nipples, and I watch them harden, as she slides her lotion covered hands across them. Then, to my surprise, she turns around and walks toward the window. Her bed is just under the window, but the way I've positioned the blinds, I can't see it very well. It doesn't matter, because what she does next, makes me shoot my load all over the shrubbery.

When she gets close to the bed, she squeezes more lotion onto her hand, lifts her right foot up on the edge of the bed and rubs lotion on her leg. Fuck! I can't believe my luck! From my vantage point outside her window, looking under the blinds, I'm staring right into her fucking pussy! As she shifts her leg around, rubbing in the lotion, her pussy looks like it has a life of its own. I watch her pussy lips opening and closing, moving her patch of blonde hair back and forth as she rubs lotion up and down her legs.

I'm about four feet away from the most amazing sight I've ever seen. My cock is rock hard and I'm pumping it furiously. As she leans forward to rub lotion on her ankles, her tits hang down like cones and her nipples are pointing straight down toward her bed. When she finishes with her left leg and is lifting her right leg onto the bed, I can't take it any longer and shoot my load on the ground and the surrounding shrubbery. I finish watching her rub the lotion on her leg and when she starts to get dressed, I run into the house and into my bedroom to change clothes.

Over the next two months, I shoot a lot of cum outside her window. I make a few strategic adjustments to her blinds and even bring out the digital camcorder a few times. Watching a video doesn't come close to the live action, and I know I can see her change anytime, so I erase the video to avoid getting caught. I think I can explain being on the side of the house, but if I was ever caught with a video of my naked sister, I think my dad would kill me. I've occasionally watched her get dressed to go out, but nothing compares to watching her come out of the swimming pool and rubbing on lotion - and she does it every time.

Until now, my sister and I have never discussed our individual sexual activities with each other. Occasionally, she asks me questions about sex or things she's heard about at school and I answer her as best I can. A military father can be pretty strict, especially with a daughter, and Lisa was not allowed to date until she was 17. She is inexperienced and naive, and I'm pretty sure she's still a virgin. I always caution her about getting sexually active too fast. I've had a few girlfriends who have been willing to experiment, so I've eaten pussy, had blowjobs and fucked a few times. But at 18 years old, in a new High School, I haven't been getting any action lately.

Since I don't have a steady girlfriend, I'm making do with my own hand outside my sister's window pretty regularly. Don't get me wrong, it's a great show, but I'm getting really horny and starting to think about my sister's body in ways that a brother shouldn't. I find myself wanting to do more than just watch. I want to touch her. I kept fantasizing that she knows I'm out here and she's putting on a show for me. I know it isn't true, but it fuels my desire to touch her and have her touch me.

One afternoon when we're alone, I head around the house because my sister has suggested we go for a swim. I'm in my swimsuit and want to get a quick look at her naked body before we get in the pool. By the time I get outside her window, she is down to her bra and panties. This happens quite often now, because I know how long I can take to change into my swimsuit and get around the house to see her naked. Her tits bounce a couple of times as she slips off her bra and I can't help but rub my cock through my swimsuit. She bends over to take her panties off and I get a great side view of her tits hanging down. Her tits look like round little cones, hanging there, with her nipples pointing toward the floor.

God, how I want to touch and suck her tits and make her nipples hard! I pull my cock out of my swimsuit; slowly stroke the length of it, as she turns around to get her swimsuit out of her dresser. When she bends over to pull her swimsuit bottom on, I see her tight, round ass and her small pussy lips hanging down. I fantasize about what it would feel like to slide my cock between those lips, while she is bent over like that, burying myself deep inside her tight, virgin snatch.

As she finishes putting her swimsuit on and is opening her bedroom door, I tuck my cock back in my swimsuit and turn toward the pool. The sound of her cell phone makes me turn back. I watch as she talks, but I can't hear what she's saying. She's getting really upset, walking back and forth as she talks to whoever it is. After a couple of minutes she closes her phone and throws herself on her bed, crying.

I love my sister and despite the perverted nature of my fantasies. I don't ever want to see her hurt. I want to know what's wrong and help make it better. I go into the house, trying to figure out a way to approach her, without giving away how I know she's upset. Fortunately, she left her bedroom door open when she went back to answer her phone. As I peek in, I see my sister lying on the bed, her head buried in a pillow and I can hear her sobbing. As I watch her body heaving up and down on the bed, I walk in and asked her what's wrong.

"It's not fair!" she says, between sobs. "That's what's wrong!" She turns toward me and lifts herself up on her elbow. Her swimsuit top has slid to the side and I can see her nipple poking out over the top of the material.

"What's not fair?" I ask, trying to focus on her face, instead of her half-naked body.

"It's not fair that girls have to walk such a fine line all the time," she cries. "What do guys want? I can't figure out what I'm supposed to do. If we let them fuck us, we're sluts. If we don't let them fuck us, we're prick teases and if we don't let them touch us at all, we're frigid. What the fuck am I suppose to do?" She turns her face back into the pillow and begins sobbing harder.

I watch her lying there crying, trying to figure out what to say and how I can help her. As I walk over and sit on the edge of her bed, I can't help but notice how her swimsuit bottom has ridden up into the crack of her sweet, round ass. Remember, I've just seen her naked and have been stroking my cock outside her window.

I wonder who was on the phone, but as I'm about to ask her, I recall that I shouldn't even know about the phone call.

"What happened, Lisa? What brought this up?" I start rubbing her bare back, trying to comfort her.

"Tony broke up with me." I hear her muffled words through the pillow. "I bet he's going to start seeing that slut, Barbara." I'm surprised. I thought Tony and Lisa were a great couple. Lisa started dating Tony right after we moved here and they've been dating steadily for the past month.

"When did this happen?" I ask, remembering that I'm not supposed to know about the phone call.

"Just now," she says, continuing to sob into the pillow. She turns her head toward me and continues. "He called me and gave me some bullshit about us being too young to get serious and that we should start seeing other people, but I know it's because I wouldn't do this!" she yells, flopping over on her back and spreading her legs apart on the bed.

I'm speechless looking at my sister lying there next to me in her skimpy swimsuit, spreading her legs wide apart and giving me an unobstructed view of her barely covered crotch. A couple of pubic hairs are peeking out from the sides of her swimsuit bottom, which is stretched tightly across her pussy lips, leaving very little to my imagination. Since I've been looking at her pussy for a couple of months, I don't have to imagine much, and my cock is beginning to stir inside my swimsuit.

"I mean it's really not fair! Have you ever dumped a girl just because she wouldn't let you fuck her?" She is looking up at me with her innocent eyes, all red and puffy from crying. She pulls her legs back together and adjusts her swimsuit top to cover her nipple. "Well, have you?" she asks softly, sniffing back her tears.

"No, I haven't and Tony probably hasn't either. Maybe he really does think you guys are too young. Or maybe he's just not sure what he wants." I'm trying to be as consoling as I can and I'm telling the truth about not dumping anyone.

"No! He really wants to fuck me," she responds. "He told me so last night, but I said no! Maybe I'm wrong. Maybe I should have let him have what he wants. God knows I wanted to fuck him, too. I was so hot and so wet it was just as hard for me to stop as it was for him." As she's saying this, my sister turns on her side toward me and starts crying again.

"I've just always wanted the first time to be with 'THE ONE'. You know? And I like Tony a lot, but I'm not sure I love him or that he's 'THE ONE'. What do you think Jack, should I have just let him fuck me? Would that have made me a slut? I try so hard to let him do what he wants without becoming a prick tease."

I reach over and put my arm around her and she starts sobbing into my shoulder. I lie down beside her and hold her close while she cries. As I'm lying there, I'm becoming increasingly aware that I'm on my sister's bed, we're both in swimsuits, which leaves a lot of bare skin contact, and I'm holding her in my arms, while she talks about whether to fuck her boyfriend.

"Well, should I have?" she asks again, pulling her head back from my shoulder so she can look at my face. We're still holding each other, as I'm trying to decide what to tell my sister.

"No, you made the right decision. You're still young." I hesitate before I start speaking again. Picturing my sister being touched by Tony and her pussy getting hot and wet to the point where she doesn't want to stop, makes my cock stiffen and I slide my hips back a little so she won't notice.

"But maybe, you know, you're teasing him a little more than you realize," I finally say.

"What do you mean?" She leans back away from me, giving me a clear view of the front of her body. She has a puzzled look on her face and I'm trying hard to keep my eyes on her face.

"Well, I'm not sure, but when you said you stopped when you really didn't want to, what had you two been doing, exactly?" I really want to help my sister, but I also want to hear the details about what her and Tony had been doing. I'm thinking I can kill two birds with one stone.

"I'm not going to describe what we were doing, Jack. Let's just leave it at the fact that I was very hot, but I pulled back in time and the next day he dumped me." Her face is a little red and it's obvious she's embarrassed about what we're talking about. She's still leaning back and looking at my face.

"Look Sis, I'm not trying to pry into your love life, but I think maybe you could use a guy's perspective on this. You think you're not being a prick tease, but as a guy, sometimes you get to a certain point, where you really can't turn back. If you stopped, I can guarantee that Tony went home and jacked-off, thinking about what it would have been like. I've been out with several girls who didn't let me fuck them, but didn't send me home to jack off. Maybe if I know what you've been doing, I could offer you some suggestions on how you can help him get relief and still save your virginity." I'm really trying to help my sister, but I'm also starting to fantasize about teaching her some sexual techniques to keep her boyfriend happy. You know, I could let her practice with me so she won't be fumbling around when the important time comes.

"Suggestions?" she asks. "What kind of suggestions?" She's still lying in my arms on her bed. She settles back down against my shoulder and I can tell she's really thinking about what I've said.

"Well, I don't know yet. I don't know what you guys have been doing. And maybe Tony wasn't all that frustrated when he went home last night. But from what you're telling me, you think he's dumping you to get laid and I think I can help you with that, if you want him back." As I say this, I have my right arm around her shoulder and I'm rubbing her back. My left hand is stroking her hair.

"I do want him back. I just don't know what to do." Her right hand is running up and down my bare side and my cock is stirring again.

"Why don't you just tell me about last night? How far did you go and what did you do? Then we can see if I have any ideas for you, okay?"

"Okay, I guess that makes sense." She snuggles in closer to me and continues to run her hand up and down my back and my side.

"Well, you know I told Mom I was going to the library with Sophie? Well, I did go there, but Tony met us and he and I went around the side of the library and sat in his car. It's dark there and we knew no one would bother us. We started kissing and rubbing against each other and generally steaming up the windows. Tony was rubbing my crotch on the outside of my shorts and I was kissing him really hard with my tongue. After a while Tony moved his hand up under my shirt and was rubbing my tits through my bra. The last few times we went out, I let him play with my tits, so I wasn't surprised when a few minutes later he unhooked my bra and pushed it up out of the way. He usually plays with my tits and my nipples, and then starts to move his hand down into my pants. That's when I normally stop him. But this time, he kept playing with my tits and pinching and pulling my nipples until I was so turned on I could feel myself getting really wet. This is the first time he's pinched my nipples like that and he just kept on playing with my tits and pinching and pulling my nipples for a long time. It felt really good."

"I was so hot that I didn't notice he'd unsnapped my shorts, until he slid his hand down inside my panties. It happened so fast and I was so wet that in one, quick motion his hand was inside my panties and his finger had slipped inside me. I was surprised by how good it felt, and I was so turned on, that I just kept kissing him. He had unbuttoned his shirt and he stopped playing with my tits to pull me against him. I could feel my hard nipples rubbing against his chest as he moved his finger in and out of me. God, Jack I have never felt anything like that. I was pushing my tongue in his mouth as far as I could and bouncing up and down like crazy on his finger while my nipples kept rubbing against his chest."

As you can imagine, her story has really turned me on. I'm hiding a raging hard-on and I notice Lisa's nipples have gotten hard inside her swimsuit, and are now pushing against my chest. I can feel her breathing heavier and she keeps moving her leg up and down, rubbing her thighs together. It seems she's gotten herself pretty worked up, too.

"It was like I was totally out of control," she continues, "until he stopped kissing me and whispered in my ear that he really loved me and wanted me so bad.

'Lisa. I really need you, right now. Let's do it tonight.' He breathed in my ear.

I was panting, but I told him no. 'Don't do this, Tony.' I said. 'You know how I feel about it.'

'Oh, come on Lisa, it'll feel a lot better than my finger and you know you really want to.'

And of course, he was right, I really wanted him to fuck me. And you know what's funny? If he had just kept going and had done it, I probably wouldn't have stopped him. I was that hot for him. But somehow talking about it brought me back to my senses. I stopped bouncing up and down on his finger. Instead I pushed myself down as hard as I could and squeezed my legs together, keeping his finger inside me the whole time we were talking. Anyway, we sort of argued about it and he finally gave in.

'Fine, I understand. It's okay. I'm sorry I pushed you, Lisa' He pulled his finger out of me and I felt so empty. We straightened up our clothes and I went back in the library to find Sophie. Then today, he calls with this we're too young bullshit. So what do you think, Jack? Can you help me?"

A plan was starting to formulate in my mind as she was telling me about her and Tony. Or maybe it was just a fantasy instead of a plan, but I was ready to start moving toward it, cautiously.

"Shit, Lisa!" I answer, nearly out of breath. "No doubt that Tony had to jack himself off when he got home. Hell, I got turned on just listening to you talk about it. And I can definitely see why you think Tony will be looking for the easiest girl in school to take out real soon. But it doesn't have to be that way. You didn't mention whether you had been touching or rubbing Tony at all. Were you?"

"You mean rubbing his dick? No, I've never touched him because I thought that would really make me a prick tease." She sounds kind of sheepish talking into my neck. I'm still stroking her hair.

"Well, guys aren't always sure what a girl will do and I'm not really sure my idea will work, if you're afraid to touch him." Part one of my plan/fantasy depends on her answer.

"I'm not afraid to touch him!" she retorts emphatically. "I just said I've never done it. I thought it would be teasing too much. Anyway what's your idea?" I was hoping she would say that, but I'm still not sure if I can pull this off. I choose my next words very carefully.

"Lisa, let's look at your situation. First, there are quite a few girls at school, sluts as you call them, who will let guys like Tony go all the way. Second, guys like Tony have sexual needs and will do pretty much anything to get those needs satisfied. Although, I really think Tony would rather satisfy his needs with you. Third, you want Tony back but you're not ready to take that big step. I think I have an answer for both of you, but I'm not sure you're ready for it."

"What? What's your idea, Jack? I'll decide whether I'm ready or not." She pulls her head back so she can look at me and I have a clear view of her left breast down her swimsuit top. Her nipple is very hard and I again have to force myself to look in her eyes.

"Lisa, what is the one thing that guys want more than anything else?"

"To get laid," she answers quickly, still staring at me.

"Nope. Of course, all guys want to get laid, but what they want more than anything else is a great blowjob. A great blowjob is every guy's fantasy. Trust me." I keep looking right in her eyes, sort of questioningly, to see if she's getting my drift. She looks at me for a while, and then I see her thinking about it. She lays her head back down on my shoulder and doesn't say anything.

"Think about it, Lisa. You don't have to give up your virginity and Tony doesn't have to go home and get himself off. Or worse, get it somewhere else. All you have to do to get him back is give him the blowjob of his life."

She speaks into my neck and I can barely hear her, but her words are music to my ears. "I don't know how," she mumbles. "I've never even touched him. How would I know how to give a blowjob and how could I be sure it's good enough to make him forget about Barbara, the slut?"

"You could learn." I decide to offer her a bunch of unlikely choices to make her think of the best way to learn. "You could, um, watch porn videos with blowjobs in them, although they're pretty fake. You could go out with other guys and practice until you're ready for Tony. Of course, getting a reputation as a blowjob queen is probably worse than being a slut. Well, I don't know, but a lot of girls do it, how hard can it be?" Here is where my fantasy will become reality or remain a fantasy. I just hold her tight and wait.

"Jack?" she speaks quietly into my neck.

"Yeah?" I'm trying to remain calm, but I have a feeling that my fantasy is just a breath away from coming true.

"I could practice on you," she suggests.

Yes! Now to put up a little resistance so she really has to beg me.

"What!" I yell, trying to sound shocked. "Lisa, we're brother and sister. We can't do that." I sound pretty sincere, too.

"Come on, Jack. You said you wanted to help me and I can't just start with Tony. What if I gag the first time or don't do it right? This was your idea and how else am I going to learn? Please."

Well, what can I do? My hot, sexy, twin sister wants to practice blowjobs on me. My cock is so hard by this point that I can barely hide it.

"Okay, but just until you get it perfected, because I still think it's weird."

"Thank you! I love you Jack!" She throws her arms around me and presses her firm tits against my chest, while kissing my cheek. Then, she sits up quickly, smiling at me. "When can we start?"

I watch her tits bounce inside her swimsuit, as she sits up.

"First, let's talk about exactly what we're going to do," I answer. "If you want real practice, we need to make it like I'm Tony. We'll have to kiss and feel each other up. I mean, you can't just call up Tony and invite him over for a blowjob; you'll have to get him worked up like before. You also have to be able to maintain your limits like before, too. So you need to practice getting as worked up as you were when you said you would have let Tony fuck you. Even after a blowjob, he may still want to fuck you. You have to be able to resist, even when you are really hot for it. Are you alright with all of this?"