Way back in the summer of 1978 my family at the time moved in to the brand new house my parents had built. It was my 15th birthday that day. My oldest sister had gotten married and moved out so it was just me, my little sister and mom and dad. This was a tri-level house where you entered on the mid level, which had our kitchen, dining room and living room, from there you could either go upstairs to the bedrooms, 3 of them or one of the 2 bathrooms or down into the family room. There was also a basement under the mid-level part.

Upstairs, there was the master bedroom and bath for my parents on the left, the main bathroom for my sister and I and guests in front of you and my bedroom first then my sisters bedroom. Our bedrooms were in the front of the house, the master at the rear and a 2 car garage below. There was a short roof section in front of bedrooms that was easily accessed by opening the window and removing the screen

I learned the first week how easy it was as I had to help dad hook our TV antenna up and we mounted it to the side of the house above the roof and went out on the roof through my bedroom window.

Being a horny young teenager (VERY horny, lol) it occured to me that the roof could be a good place to jerk off in public so early on I would climb out there late at night with my hard cock waving in the breeze and jerk off. Sometimes I would stand, others I would sit.

After a couple of years doing this my sister asked me one day to show her how to climb on the roof too. I did without even wondering or asking why she wanted to know. I found out that night. She had been hearing me climbing out at night and was curious but not long before she had seen me jerking off. That night she climbed out too just after I got started beating the meat.I quickly stopped when I heard her climbing out and was surprised that she was naked too.

Seeing each other naked wasn't a huge deal as my family was sort of closet nudists. We would walk naked from bedroom to bathroom etc. But, as far as I knew, this was the first time she would have seen me masturbating or even with an erection. We sat there talking a few minutes when she asked me why I stopped jerking off. I denied doing it but she laughed and said she had seen me and wanted to watch.

I was still rock hard, dripping precum, and unsuccessfully trying to hide it although I thought I was getting that done. Anyway, she reached over and grabbed on and said if I wasn't going to jerk it she would. I didn't last long, I shot ropes a minute later. That wasn't the end of that night though. My erection never went down so I started masturbating again which got her rubbing her pussy. I could hear how wet she was so I, figuring turn about was fair play, reached over and stuck 2 fingers in her and started moving them in and out while circling her clit with my thumb. She quickly came as well saying no one had ever made her cum that hard so far in her life. She was not a virgin anymore I knew. We kept messing around for 2 more hours giving each other a couple more orgasms each before heading in to bed.

That was the start of our sexual messing around which we still do to this day. Not as often as back then but still do.