I've been reading this site for some time but I have never posted any stories until now.
We went on vacation just a few months ago, me and my wife and her three others sisters. We only had two rooms rented so my two sister- in-law's shared the other room and me and my wife and their youngest stayed with us on one bed. When we slept, I couldn't help noticing that my sister-in-law was not wearing a bra underneath her pyjamas.
While my wife was facing me, asleep, I stretched my hand out, long enough to reach my sis-in-law's breasts. I felt them slightly and then I tried to massage them. I was doing this while my heart was pounding to death, afraid that she might wake up. But I think she was awake and she liked what I was doing. Then my wife moved and I faced her, and that was the time my sister-in-law moved and took my hand away from her breast.
I slept for about two hours, and after that I did the same thing again. This time she allowed me to play with her a lot longer. I still cherish that memory, and every time I masturbate I keep on thinking about her. I wish we could go on vacation again and do more next time.