You Show Me Yours and I'll Show You Mine
by Ashley
Copyright© 2025 by Ashley
Incest Sex Story: How many brothers and sisters have gone through that rite of passage? A lot, I suspect. But with most, it stops there. But circumstances conspire so that Cassie and Shaun see each other again and again as they both get older. Like it's fate, or something...
Caution: This Incest Sex Story contains strong sexual content, including mt/ft Consensual Heterosexual Fiction Incest Brother Sister First Masturbation Oral Sex Petting Tit-Fucking .
The first time that I saw my little brother’s penis, I didn’t know what it was called or what it was for. I’d been nine, which meant Shaun must have been seven.
We’d been fooling around in my room one Sunday morning, when I’d seen ... something through the fly of his PJs.
“What’s that?” I asked, pointing at his groin.
“What’s what?” he replied, looking down.
“Between your legs. You haven’t got ... what I’ve got.”
“Well, what have you got?”
Then I uttered those words, variants of which must have been spoken millions of times, in hundreds of languages, all across the world: “You show me yours and I’ll show you mine.”
“Promise?” he asked, probably because I had been known to cheat at that age. I crossed my heart with a finger, and he pushed his pajama bottoms down to his knees. I peered intently, bending a little at the waist for a better view. It was a sort of wrinkled little sausage resting on top of a fleshy bag. It put me in mind of a bald little mouse, and I thought it looked kinda cute. I wondered what it would feel like if I touched it, but I had a vague sense that we were being naughty already, and I didn’t think I’d better.
“Your turn,” he said impatiently, getting bored. I slid my bottoms down to my ankles and then stood up.
“Oh,” he said, sounding disappointed. “You haven’t got much, have you?” He bent down to look closer. “Where do you pee?”
I waved vaguely at the slit. “You pee out of the end of ... that thing, do you?” I asked, pointing at the little mouse.
“Yup.”
“OK,” I said, completely satisfied. “What shall we do now?”
“Breakfast!”
And that had been that. PJs back up. The whole episode forgotten. Well, almost.
The second occasion started badly. There’d been a scream from the kitchen, and Dad had rushed out to see what was going on. When he came back, his face was white. “Go upstairs and grab some things, toothbrush, clean clothes, underwear,” he said, looking panicked. I’d never seen him like that, and it scared me half to death. “What’s going on, Dad?” I asked.
“It’ll be fine ... but your mom’s cut her hand, quite badly. She’s got to go to the hospital, and I’ll drop you at your aunt’s on the way. Go on. Go on. Quick as you can.” He wasn’t quite shouting at us, but I could tell it was close.
It was all very scary. Mom had a worryingly bloody kitchen towel wrapped around her hand, and looked as pale as Dad did. He drove a lot faster than normal, and Aunt Brenda was already waiting on the sidewalk as we pulled up.
“Come on, sweethearts,” she said, ushering me and Shaun out of the car before waving Mom and Dad off.
Shaun looked petrified - much younger than his fourteen years - and stood close to Aunt Brenda for comfort. “Is Mommy going to be OK?” he asked, sounding very worried.
She put her arm around him. “She’ll be fine. But she will need some stitches. They’ll probably be a while, so you’ll be staying with me tonight.”
She made us some pasta and, when we’d eaten, she said that we should get ready for bed. We’d never stayed over at her apartment before because she only had one bedroom.
“You and Shaun can have my room and I’ll sleep on the couch,” she said. I wasn’t sure how I felt about that, and I guess that it showed on my face. “Don’t worry, my bed is two singles, we’ll just pull them apart.” Having done that, we all made up the beds.
“Right, baths!” Brenda declared. “You first.” And she pointed at me.
“Bath?” I asked. I couldn’t remember the last time that I’d had a bath.
“Yep, I don’t have a shower. Off you go.”
I bathed, which I actually quite enjoyed, then put my nightie on and got into bed.
I was still awake when Shaun came in from the bathroom, and I saw his pajama bottoms sticking out in the front. I was a lot more worldly-wise than I’d been the last time, but I was curious.
“Why have you got a boner?” I asked, my eyebrows raised as I looked pointedly at his groin.
He had the decency to look a bit sheepish. “I was playing with myself in the bath,” he admitted.
“Pervert,” I said, but fondly. I’d seen a few pictures of erect penises in some porn, but strongly suspected that those were far from normal, just like some of the comically large breasts. I’d never seen one in real life, and now one was right in front of me, making me feel all tingly, and I really wanted to. “Can I see it?” I asked softly.
“Only if--”
“Yeah, yeah, yeah,” I interrupted, knowing exactly where he was going with that. I loved the way that the lump twitched and got bigger when he knew he was going to see my pussy. Again.
He came over and stood next to my bed, and I sat up to get a better look. In an echo of seven years earlier, he lowered his pajama bottoms to his knees. I had to stifle a gasp when it came into view.
The pictures of penises that I’d seen had been pretty scary: all big and red and angry-looking, and covered in thick veins. Shaun’s was hard and I guessed it was about four and a half, maybe five inches long, but the skin looked soft and nice, except for a bright pink shiny bit, peeking out of a wrinkled collar. I thought it looked lovely, and the tingling in my pussy got much stronger.
“Wow, that’s a lot bigger than last time I saw it,” I said, and giggled as it twitched and a bit more of the tip poked out. I glanced up briefly, and he was grinning and looking incredibly proud, which I thought was absolutely adorable. I licked my lips as I imagined how it would feel to touch it ... or kiss it ... or even to lick it. My wickedly naughty thoughts made me shiver.
When it gave a big twitch, I looked up at him again, and he shrugged. “I think it likes you looking at it,” he said in an amused whisper.
He let me stare at it for the longest time, while I got more and more excited, and I even began to feel a bit moist inside, maybe for the first time. It was almost a shock when he finally said softly, “Your turn.”
When I first realized that I was going to have to let him see my pussy, I’d been a little nervous. But now I was so turned on that I couldn’t wait to push my bedclothes down, and pull my nightie up, even parting my legs a little so he’d be able to see better.
His silence and his intense gaze made me begin to feel a little self-conscious. I thought my pussy was lovely, but he was the first other person to see it since I was a kid, and suddenly my chest felt tight with apprehension.
“Well?” I whispered, when I couldn’t bear it any longer.
He took a long, shuddering breath. “It’s lovely,” he said, the words barely audible. “I thought it was pretty before, but now ... and I love that little bit of ... fur.”
It was the perfect thing to say, and I wanted more than anything to cuddle him, but I knew that that would have been a terrible idea.
“Time the light was out, you two!” Brenda yelled from the corridor.
I turned over to put out the bedside light, and when I turned back, he was still there, lit by moonlight coming in through the thin curtains. If anything, he was even harder, and I could see the whole tip, like a shiny pink mushroom. It looked lovely, and I stared at it with only one thought in my mind. “Can I touch it?” I heard a voice ask that sounded very much like mine.
“Yes,” he answered instantly. I waited for the inevitable condition, but none came.
I reached out and stroked a single fingertip up and down the side. It was just as soft as it looked, and I giggled when it bobbed around like crazy. Shaun made a funny sort of humming, slash whimpering noise, so I figured he liked what I was doing. I knew that I should stop - Brenda could come in at any moment - but I really wanted to touch the shiny tip.
His hips sort of shimmied as my fingertip brushed over the edge onto the end. “Oh God, Cassie. That feels so good,” he moaned. It was just as silky as it looked, but it was how warm it was that stunned me. I loved it, and I could have kept stroking him for ages, but the longer we carried on, the greater the risk that we’d get caught. Besides, he hadn’t touched me, and I really, really wanted him to.
“I think I’d better stop now,” I whispered, very reluctantly, and then drew my hand slowly away.
“Awww,” he whined, clearly disappointed, but he tucked his erection away and started to turn around.
“Shaun,” I said softly, taking his hand, and he turned back. “Don’t you want to touch me?”
His face lit up like it was Christmas. “Really? I-I-I didn’t think you’d let me,” he stammered, grinning down at me.
God, he was so, so sweet that it actually gave me a pain in my chest. “It feels good to me, too,” I explained as I placed his hand over my pussy.
“Oh, my God, Cassie. It’s so, so soft,” he said, brushing his fingertips over my nearly bald vulva. His eyes were wide, and the bulge in his PJs started growing again. “Is it alright if--” he began.
“Yes,” I interrupted, not really caring what he was going to say next. “Just be gentle.”
Having someone else touch me there sent thrills right through me that made it difficult to breathe, and I sat there making tiny shuddering gasps as his soft caresses made my head spin. His fingertip, brushing along my slit, was affecting me like nothing I’d ever known before, and I absolutely adored it.
Then we heard Brenda’s footsteps coming along the corridor, and he snatched his hand away and crept quickly back to his own bed.
I lay there with my heart pounding and my pussy tingling like crazy, wanting nothing more than to go to Shaun’s bed and slip under the covers and carry on from where we left off.
It was ages before I finally got to sleep.
When I woke up in the morning, Shaun was already awake and was smiling at me. All sorts of things went through my head, wondering if he wanted to talk about what had happened, but he just wished me a good morning.
“Shall we find out if Mom’s OK?” I suggested.
“Yeah,” he replied, and we jumped out of bed and headed off to find Aunt Brenda. Mom was fine, but she’d had ten stitches, and ended up with an impressive scar on her palm.
There was never any awkwardness between us afterward, even though we didn’t speak about it until years later. Being older, I knew I should have felt guilty about what we’d done, but Shaun gave no indication that he hadn’t enjoyed every second, and I’d absolutely loved it. The guilt wasn’t enough to stop me from regularly masturbating to the memory of that night, though, and I strongly suspected that he did too.
As we got older, I couldn’t help but notice how nicely my little brother was filling out, and, when he was fifteen, he was as tall as me, and getting quite broad across the shoulders.
I tried hard to ignore the warmth that began to spread out from my belly every time that I saw him, putting it down to the fact that I’d seen and stroked his erect penis. Then I’d wonder if it had grown in proportion to the rest of him, and then have to try to get that image out of my head. Well, until I was alone in my bed, anyway.
I began to have intensely erotic dreams about him, often beginning in the same way as that night, but in my dreams, I’d take him into my mouth while his fingers slipped inside me. Mostly, I woke up at that point with a racing pulse and gasping breaths, and with damp underwear. Often I’d masturbate, imagining how it would feel to have him twitching and throbbing inside me, as my fingers sought out my clit and I drove myself to a shuddering climax.
The first time that I held another boy’s cock in my hand, it was in a furtive mutual masturbation session in his room; his parents were downstairs, so we didn’t dare undress. While I was touching him, I couldn’t help thinking about Shaun, and how I wished it were his penis. He came very quickly, and then lost all interest in pleasing me. Which was maybe just as well, really, because he didn’t know what he was doing, and wasn’t very gentle. I didn’t see him again.
Rather than taking my mind off Shaun, it only increased my longing for him, even if just to see it again. When it finally happened, it was by pure chance.
One school day morning, Mom sent me to wake Shaun up after he’d clearly gone back to sleep. When I opened his door, my cry for him to wake up died on my lips. He’d pushed the covers off and was naked, and his cock was lying on his belly, maybe not fully erect, but not far off. It was bigger than before, both longer and thicker, and if anything, even more beautiful.
The bulbous tip was fully exposed, and I found myself licking my lips as I gazed at its velvety-looking skin. I could see thick veins running up the shaft, and when I got a little closer, I fancied I could see them throbbing with his pulse.
The knowledge that he could wake up at any moment was the only thing that stopped me from touching myself, and I just stood there until he frightened me by making a soft grunting noise and moving slightly in his sleep. I crept backwards to the door, and, with one long final look, knowing it might well be my last, I left and closed the door behind me.
“Time to get up, Shaun,” I called out as I banged on his door.
Pretty much every school day morning after that, I’d watch the clock in the kitchen, hoping that he’d oversleep again. It was nearly two weeks before it happened, and I said, as casually as I could manage, “Tsk, am I going to have to wake up sleepy-head again, Mom?”
When I quietly opened the door to his room, I was sad to see that he was covered up from the waist down. I went and stood next to the bed, and could see a bulge in the covers. I stood there for maybe a minute, looking at that lump while the needy little ache of desire between my legs got stronger and stronger.
In the end, I couldn’t resist it. I checked his breathing, which was still slow and even, and then reached out with trembling hands and grasped the top of the covers with my fingertips. I held my breath as I pulled them down as slowly as I could. The tip appeared first, all tight and shiny, and almost purple with all the blood pumping through it.
I almost stopped there, but he still seemed fast asleep, so I carried on until I could see his balls, all heavy-looking and lovely. I pressed two fingers over my clit and rubbed gently as I tried to commit each tiny detail to memory. I wanted desperately to touch him again, to feel what the smooth skin of his glans felt like, or the soft, thickly-veined skin of the shaft, or the wrinkled skin of his scrotum, but I didn’t dare.
I stood there for ages, my pussy muscles clenching madly, loving the way that his cock twitched and bobbed, and once again wondered what it would feel like if it was doing that inside me.
Finally, my fear of being caught outweighed my lust, and with massive regret, I pulled the covers over him and took a few steps back. “Wake up, Shaun, you’re going to be late.” He looked so cute as he rubbed the sleep from his eyes, and then he must have realized that he had a hard-on, and I could see him beginning to panic, until he looked down and saw that he was covered up.
What I’d done scared the hell out of me. What if he’d woken up and caught me diddling myself? What if Mom or Dad had walked in?! I decided that it had to stop. I still found myself glancing up at the clock in the mornings, but if I did have to wake him up, I did it by knocking on his door, while ignoring the tingly itchiness that I got just from the memories that it provoked.
I threw myself into dating, not altogether successfully.
I ended up giving my cherry to a guy called Simon, not long after my seventeenth birthday. He was a nice boy, kind and funny, and ridiculously grateful. I’d put myself on the pill a few months earlier, determined that I was going to do it, partly because I was horny, and I wanted to know what it was like to have a boy’s cock inside me, but mostly in the hope that it might stop me thinking about Shaun all the time. It didn’t work; in fact, I was actually thinking about him as Simon was fucking me. It was nice enough, but it wasn’t fireworks. It wasn’t Shaun. I broke up with him not too long after; it didn’t seem fair on him somehow.
Apart from a few one-night stands, that was about it until I graduated from high school. I wanted to go on to study Physical Therapy, but there was no way we could afford for me to stay on campus anywhere. Fortunately, there was a pretty good college that was close enough that I could stay at home, so I enrolled there.
I can’t say that I forgot about my little brother; that was hard when I saw him most days, and he kept getting more and more buff, but some hook-ups at college over the first six months at least distracted me. And the studying, obviously.
I arrived home around lunchtime one Saturday, having stayed over at a friend’s after a party the night before.
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