I've had an ongoing relationship with my sis for 18 years.
My family was a pretty prudish bunch of people. Any sexual talk was forbidden, and we we're told that any form of sexual contact outside of marriage and for the purpose of procreation was dirty and wrong. Needless to say, masturbation was wrong too. But being a 12-year-old boy I really didn't care, I just hid it better. As kids we used to spend part of our summers at my grandparents house and that's where this wonderful event with my little (two years younger) sister happened.
My grandparents had gone to town for the afternoon leaving me with my sister Ann. It was hot and pretty nasty out so we were in the bedroom we shared since it had an airconditioner in it. As we sat there Ann, completely out of the blue asked me if I wanted to see between her legs. I was pretty shocked and asked her why she would ask that. She had said her friend Charlie had showed her between her legs earlier that summer and had asked if Ann had seen what I had between my legs. Apparently Charlie and her brother would play with each other so Ann thought she should offer to show me. I said ok and she just took off her pants and underwear and laid on the bed. I got down and put my face about two inches from her little puss and just stared at it. It was so pretty, all puffy with no hair, her inner lips stuck out just a little, just perfect. After a few minutes she asked if she could see me. I agreed and took off my pants and under wear and my boner just sprung out. She studied it and asked questions like, 'is it always sticking out like that?', or 'does it bend?' Then she asked if I touched it when no one was around. She said that Charlie touched her spot and her brother would touch himself or they would touch each other. I told her I stroked it and started doing it. She watched as I pounded away at it until I came. At the time I was only shooting a drop or two but it felt good. She then showed me what Charlie had taught her. She spit on her fingers and started rubbing her little slit. She did it for what seemed forever. I stopped her and asked if I could touch it, she said yes so I started fingering her, it was amazing! After a while she said she wanted to jerk me and I let her. She was about as clumsy stroking cock as I was at fingering pussy but it was great.
We soon heard a car coming and got dressed and went out to meet our grandparents. We continued to touch each other in a similar fashion for about a year before things got really hot but I'll save that for another time.