Had sex with my sister
I was 19 and had been broken up with my girlfriend for about 2 months. I came home to find my 15 year old sister and her twin best friends in our pool smoking some weed. I joined their party and started entertaining the girls. Then I became a big hero when I bought beer. As the night went on we talked bout skinny dipping. Eventually I made my move on one of the girls. we went up to my bedroom and when it got down to it, I discovered she was having her period. So a little while later I turned my attention to her twin, only to find she was also having her period.
After the girls left, my sister and I went up to my room and smoked a joint. I asked if she wanted a shotgun, and as I was blowing smoke in her mouth our lips touched. I do't know why but I then kissed her. She didn't stop me, but didn't enthusiastically kiss me back. After a little while of awkwardness, I started talking about how much she changed over the years, and how big her tits were. I asked if I could see them and she pull her shirt up. I then started touching her, and sucking on her nipples, she really got off on it. Next thing you know we were rolling around and well we fucked. We never did it again and never talked about it. Sometimes I feel guilty and some times it seems really erotic.