Hi! I’m Philip and I’m seventeen when this tale begins. I really like all kinds of science, math, and sex. Not necessarily in that order either. The scientist I want to be pushes me to learn all I can about things I like. There is so much “wonder” in the universe. Women’s bodies, and what us men can do with them, are only part of the mystery but that is what this story concerns.

As this story opens I am a pretty ignorant but horny virgin. I’m with my eighteen-year-old step-sister Mary Beth at a nudist resort. Our parents met here and just got married. This was their honeymoon so we left them alone as much as we could.

Anyway, we were sitting in a beach shelter at the beach on the adult side of the resort when a nice looking guy about our age approached us and introduced himself as Sam. We learned that he was here with an extended family but they were all busy and he wanted to meet some folks his own age.

We swam and sunned and visited for a while. Sam was pretty muscular and tanned all over. He was a farm boy and was apparently often without clothes at home. Mary Beth and I were rather scrawny and pale. I noticed that my step-sister looked at him a lot. His soft cock was much bigger than mine.

By the way, sixteen is the age of consent here. Mary Beth is a virgin too and we have only gone as far as making out together a little bit, mostly out of curiosity. She is nerdy like me and very unsure of herself. Besides, we are now related and wary about the incest thing.

Sam asked us what we thought about the sex activity here in the adult side of the resort. I explained our status but we were quite curious. He told us about the way it was at their place, and my pecker, as well as Mary Beth’s nipples, and probably her pussy too, got aroused.

“Would you like to learn more?” Sam offered. We nodded and led the way to our cabin. Our parents were gone so we went to the bedroom Mary Beth and I shared. Two beds.

I watched spellbound as Sam put his arms around Mary Beth and kissed her real hard. I could see when his tongue got her mouth open and I could also see how she clung more tightly to him. His hands were caressing her back and buns and hers started to do the same thing to his. They were pressed so tightly together that the head of his rising pecker appeared in back between her thighs up against her bun bottoms. She was pretty skinny.

Sam moved her to a bed and she laid back. He sat beside her and stroked her from neck to knees, not missing any important parts. Her near hand rubbed his body and found its goal, grasping the hard rod when it was encountered. Mary Beth’s breathing deepened and her face flushed as Sam stroked her thighs and finally her pussy.

She pulled his cock towards her crotch so he repositioned himself between her spread thighs and I watched spellbound as the head disappeared into her fur flanked slit. She moaned as he slipped deeper and deeper with each stroke. I sat down beside her and held one of her hands. Her other was cupping a bun of the man who was filling her.

There was no pain in the initial penetration. She later told us that she’d used her mother’s toys a lot so her hymen was long gone and she was well stretched for a man’s organ.

My other hand stroked my own erection in synch with Sam’s. I stopped before my climax but he did not. His body tightened as he shot the first sperm into my step-sister. She shuddered and moaned when she felt the deposit inside.

Mary Beth turned to look at me and said, “That was incredible! You have to try it!”

I looked at her and said, “And just who am I supposed to try it with?”

There was a pause as she realized the implications and said quietly, “Me?”

Just before he pulled out, Sam whispered, “I want you again when he is finished.” She nodded then pulled my cock towards her just like she had done to Sam.

As my cock sank into a place that was wetter, hotter, and silkier than I could ever imagine, I kissed her soundly and bent down to suck on her upturned nipples. After less than a half dozen strokes my cock exploded in the most body wrenching orgasm I ever had, before or since, I think. She didn’t come but looked lovingly at me and kissed me again. She whispered, “Did you like that?”

I thrust a couple of times with my half-deflated dick and said. “Damn straight! You are wonderful!”

Sam laid on his back and guided Mary Beth to sit on his recharged rod. He showed her how to move. After a bit I straddled his legs behind her and cupped her breasts from behind, tweaking her nipples and kissing her neck. Sam lasted a long time and she climaxed twice. He then had her lay on his chest and instructed me to enter her twat from behind.

I gave her two climaxes too before I shot the last semen load of the session all over her cervix. I didn’t want to pull out even after I shrank so small it would hardly stay in. It was dinner time by now so we took a shower together and went to the dining hall.

Sam was introduced then he went to find his family. Mary Beth’s mom asked her what she’d been doing this afternoon and she whispered “Your little girl became woman today!” Mom gasped and said, “We have to talk later.” They took off together as soon as they could and I went for a walk on the beach.

I saw Sam talking very seriously to a slim blond girl then walk away from her, obviously unhappy. I hurried to catch up with him. We walked without talking and he suddenly said, “That was Amy. I was partnered up with her earlier but she has been screwing around pretty indiscriminately and I just couldn’t accept that any longer. No one expects to be completely monogamous here, even married couples, but she pushed it way too far. She got pregnant last year while she was here so I thought she’d learned her lesson, but I guess not. I’d like to spend some more time with you and Mary Beth if that’s ok.

For the few days that were left of our visit we’d do nonsexual stuff during the day as a threesome. Sam would do stuff with Mary Beth in the evening as a couple, like walk and screw on the beach in the moonlight, while I got to spend the night with her later in my bed. I asked her if her pussy got sore and she laughed. “I’ve used my mom’s toys a lot before we came here. It’s toughened up.”

She told me that she’d reassured her mom about being careful about pregnancy but wanted to get on birth control as soon as she got home. Her period did start a couple of days after the “big day” but it didn’t slow us down much.

My step-sister also told me that her mom was terribly envious that she had two lovers, especially for her first time. Mom had never even done two guys on the same day. Mary Beth offered me to her. Mom blushed but didn’t answer. The lack of refusal was noted by her daughter.

I later realized that this young woman was wise beyond her years. Even though I could hardly compare with Sam for physique, cock size, or skills, she always seemed eager and happy to fuck me, even after spending the evening with Sam and enjoying him who knows how many times. She delighted in showing me new things she learned and I showed my appreciation any way I could, even eating her when full of Sam’s semen.

When we got home Mary Beth got contraception, of course. She also spent every night in my bed. We were young horny lovers for sure. She frequently surprised me with something new that she’d seen on the internet. Girls can like porn too, I discovered.

One real big surprise was on my birthday. She sent me to bed early after my birthday dinner, saying my gift would be delivered there. Of course I was ready and hard in anticipation. There was candlelight in the room and I was instructed to keep my eyes closed.

I felt a body get in bed with me but the tits that pushed against me were lots different than the ones I was expecting. Fuller and softer. Then I heard Mary Beth’s mother say, “Happy birthday, I’m your present!” I damn near ejaculated right then.

My present was wrapped in a sheer nighty and I took my time unwrapping it. First I explored the magnificent rack I had often ogled at the resort. What a feast for hands and mouth. Her nipples stood up hard as they enjoyed what I did. She whimpered a bit so I knew I was doing the right things. She rolled me on my back and gave me a brief titty fuck, something that Mary Beth struggled to do. The head of my cock got brief licks in the process.

I kissed and touched my way down her body, over the nicely rounded belly and to the firm thighs that framed a furry love temple. I could smell a woman aroused. Her body was larger and fuller than the only other one I’d had my hands on. Not fat, just a lot more rounded.

She had difficulty holding still as my tongue touched her nether lips. I was quite aware of where I was as I tongued her clit and pushed into the opening where Mary Beth had exited on her birth day. My “gift” grabbed my head and pulled me on top of her. A fierce kiss accompanied a groping hand, searching for what she wanted inside of her. I slipped in easily. Not as tight as Mary Beth but wonderfully wet, hot, and soft.

She gripped me with pussy muscles I’d never experienced and I too soon shot my seed in her. She sighed, “Keep moving! I want more!” That sounded a lot like Mary Beth.

I stayed pretty firm and was soon hard again. This time I pushed against her clit and she shuddered in climax before I gave her another load. We slept wrapped up in each other and screwed again in the wee hours. I fell asleep thinking how my body was trying to create a half-sibling to my step-sister. Wouldn’t THAT be wild!

Mary Beth awoke us and said it was her turn. Mom kissed me and left as Mary Beth licked my juice covered pecker. Wow, how erotic. When I slid into her more familiar twat it was very wet and I knew she must have been with my father while I banged her mom. That thought made my tired pecker shoot a load I didn’t think it had left in it. We slept with my worn out cunt explorer soaking in all the seed she’d collected during the night. What if she had a half-sibling too? Enough of that! Pray for crop failure!

The gals decided that pussy sharing would happen only on birthdays. But then, women almost always made the pussy rules. Well, it was something special to look forward to, that was for sure.

Mary Beth and I were even hotter for each other for a while, as were Mom and Dad, I heard. Mom got her wish for two men in a row. What would she want for HER birthday?

It was almost like I had a wife. Nice steady supply of pussy and having to deal with everyday issues too. Not like dating where you could take them home and get away for a while. Pros and cons, but good training for marriage I was told.

Mary Beth had regularly been talking and emailing with Sam. She invited him to visit on her mom’s birthday. I knew immediately what that imaginative minx had in mind. A new cock record for her mom and maybe herself. Some variety for sure.

Although neither one of us ever commented on the different physical characteristics of our other sex partners, we were both teen-age insecure about our own smaller sizes. My cock and her tits. I figured Sam and my dad were better equipped than me from seeing them at the resort, but maybe I knew her body better. She rarely missed an orgasm when I fucked her and she was too polite to complain.

Sam arrived the afternoon of Mom’s birthday and the two women took him to bed almost immediately. Mary Beth had wanted to see her mom getting laid, and vice versa, so this was their chance. Dad and I drank beer in the back yard.

An hour later, looking none the worse for wear, the trio found us, somewhat the worse for beer, and dragged us out to dinner. After returning home, mother and daughter played musical beds the rest of the night. They got little sleep and us guys at least had a recovery break in the rotation. The next night was a little calmer with some different arrangements. Sam and I kept Mom supplied with cock and Dad took care of Mary Beth.

The women kissed him goodbye fondly with promises of a rematch.

“Stilt”, as he was usually referred to, was a basketball player with lots of brains. Mary Beth was taking a business class and he was her project partner. She was surprised at the depth of discussions they had and when he asked her out she was pleased.

After a couple of fun dates with him she had a sore neck looking up at him because, at six foot six, he was a foot taller than her. He was socially nerdy, which she didn’t mind, and was obviously horny. Curious to see if his male equipment was proportionate to his height, she encouraged some mutual fondling and discovered that it was. As thin as mine but much longer than any others she had felt.

The big guy asked her to the prom which she accepted only if she could double date with me. I was not much of a dater so she fixed me up with Carol, a classmate of hers.

Mary Beth had learned that Carol was quite disappointed the few times she had tried sex. My step-sister reassured her that she’d heard that I was quite skilled and worth a try. This was important because the gals decided they wanted the four of us to get a hotel room after the prom. Stilt and I were fine with that. He was a virgin, he confided in me. Girls were intimidated by his size even if they got a hold of his tool.