Having found this site, I was reminded of a superb experience, almost unique for me, which I had when I was 18. My girlfriend, J, had gone away to university for 3 years, but we still saw one another (and subsequently married). While she was away I regularly saw her family, Mum, Dad and younger Sister, V, who was 15 at the time.
V was a very attractive girl with a lovely slim figure and developing small breasts. Their family were very open, and I knew that they were happy about being naked round the house and bathrooms bedrooms etc, unlike mine which were quite prudish! Obviously when I was there they were more careful (unfortunately), and it was my fantasy to see V in the nude. I am talking about the 1970's now, and I had only ever seen 1 girl naked and that was J.
Although J and I never had sex before we married, we did masturbate one another, and of course I masturbated regularly myself, especially while she was away. V was one of my fantasies, but I could only dream of what she looked like naked.
I decided that before I had a chance of seeing her in the nude, I had to show her that I was not bothered about her seeing me, so I deliberately planned a couple of 'accidents' where she caught me in the bath or the bedroom and I openly displayed myself to her. She didn't react at all, and simply accepted me as part of the family, which was nice.
As weeks went by, and I spent a bit more time at their house V used to wander round a lot in her underwear or nightwear in front of me, and eventually an opportunity arose where she needed to take a bath while I was shaving in the bathroom. She came in to the room and calmly filled the bath, undressed and got in. I had to try not to stare, and made every excuse to stay in the room as long as possible, stealing glances at her breasts and jet black pubes. After that she was quite open about being naked in front of me, and all I had to do was not make it obvious what a turn-on for me it was; although it gave me plenty of fantasy for my wanking.
One morning after I had stayed over, in J's room, I was pleasuring myself in bed when V came into the room to get some clothes from the wardrobe. She was totally naked and calmly took some clothes out, then amazed me by coming and sitting on the edge of the bed and talking to me. After a while she joked 'come on, time you got up!' and pulled the quilt back - not expecting me to be naked in bed I'm sure. It took me by surprise, and I had no time to cover my erection. She saw my penis and was taken aback for a moment, before stating that she had never seen one hard before. She asked if I played with it, and I told her honestly that I did. She reached out to touch my penis and very gently ran a finger up the length, evidently not sure what it would feel like. She asked me if I would stroke it for her, and I agreed on condition she never ever told J. She promised, and I said that it would help me if I could see between her legs, that it would excite me more.
She agreed to sit on the bed with her knees apart and legs drawn up so that I could see the opening of her slit surrounded by those lovely pubes. As I started to wank myself, my pre-cum started to flow and I covered the head of my cock with it, rubbing harder. She was watching me intently, alternately looking at the expression on my face and my engorged penis. Her hand slowly went down to between her legs and she opened her pussy lips and exposed her clit. Then, licking her finger she wet her clit and started to rub it. She confessed that she masturbated regularly, but had never had such help as seeing an excited male in front of her! This was too much for me and I spurted my spunk over my hand and stomach. She gave a little squeal of excitement as I did so, and continued to rub herself. I leaned across and placed my hand over hers, whereupon she let me take over rubbing her little pink clit while she gently pushed a finger inside her vagina releasing her wetness. I continued rubbing until she came, quite noisily, taking the opportunity of feeling her pretty breasts and squeezing her nipples at the same time.
When she finished cumming she dashed off to the bathroom to clean up, leaving me to do the same.
Although we never indulged in mutual wanking again, we both remembered it and neither of us ever told anyone within the family about it. But even now when V, (now my sister-in-law) and I meet, we sometimes exchange a knowing smile about that wonderful occasion.