It started when I was 13 and my sister was 19.
Well for me it started when I was 13 and my sister was 18. My dad had put in an above ground pool with a home made heater in it. I found out that the heater would send hot water back into the pool through a pipe at the right height that the hot water would blow through my shorts and onto my pines and get me hard. It didn't take long before I found out that I could put my cock inside the pipe and fuck it.
One night, when our parents were out to dinner and I was in the pool playing, getting hard and just starting to fuck the pipe, my sister came out and saw what I was doing and said "WHAT ARE YOU DOING". I tried to cover up by pulling my shorts back up but she knew what I was doing and said I need to get out of the pool and follow her to the pool house or she would tell our parents what I was doing.
So I did get out and followed her. When we got there she locked the door to the pool house and then walked over to the couch where she sat down. Deb then told me to walk over to her and as I did I could see she was looking right at my outlined cock in my wet shorts. I stood in front of her and she looked up at me with a smile and said that she would finish what I had started in the pool.
With that she unzipped and pulled down my shorts and told me to step out of them. I was now standing in front of my sister nude and hard as could be. Deb took hold of my cock and started to work it over and before long she was giving me the first of many blowjobs that summer.
To this day we talk about it and we have even played a few more times and not just oral type of play, but that would be for a different place to tell you. I hope you all liked this because when I think about it and ever share this with you I get turned on and I have to go masturbate.