My gf has a sister who's pretty hot. Once when I was over there, I had an opportunity, and I snuck into the hot sister's room and stole a used thong from her dirty clothes basket. When I got home, I sniffed her thong while I jerked off and later I jerked off with her thong wrapped around my cock while thinking about her and my gf together.
Another time, I was alone with my gf at her house and she had told me that she argued with her sister. I convinced her we should fuck in her sister's bed. She liked the idea that we were sneaking around and doing something naughty. "What if someone came home and caught us?" We did a few different positions and in the end I was fucking her doggy style. I started imagining that I was fucking my gf's sister, and the next thing I knew I came about the hardest ever! The cum was literally dripping from my gf's pussy onto the bed… and instead of cleaning it up, we just put the covers up over it. :)
