I resented visiting my grandparents at their summer home when I was 15 because it interfered with my masturbation. This was soon to change.
I resented my family visited our grandparents on weekends during the summer at their country place because it interfered with my favorite Saturday masturbation. So I began wandering around the grounds looking for a place where I could hide and get in an undisturbed jack off. I finally found what my 15 year old mind thought would be the perfect place. It was an abandoned boat house about a quarter of a mile from the main house around a bend on the creek which could not be seen from it. When I thought everyone else was busy with their own activities, I'd slip away, go the boat house, strip naked, and get in a good come. This worked well for several days I believed. It turned out to have been better than I thought. Unknown to me, my cousin Lisa had the same problem, and solved it the same way. She went to the boathouse loft to tickle her clit, so I unknowingly put on show for her with my vigorous jacking on the lower level. She began acting oddly, looking at me quizzically and smiling with an air of knowing certainty. When I didn't tumble to her hints, she asked me to swim out to the float in the lake with her so we could talk. When we got there, I asked what was the big surprise. It was bigger than I expected. She started by describing what she saw me doing in the boat house, and calmed my embarrassment, saying not to worry, she was doing the same thing, and thanked me for the wonderful show which so enhanced her own orgasms. She suggested that next time, I went to the boat house I join her in the loft so we cold jack off together. Next day I did. I nearly came just from looking at her beautiful 15 year old body with its small patch of pubic hair and grapefruit sized tits.