I discovered by accident when I was about 12 years old that my 15-year-old sister masturbated every morning before getting out of bed. This occured in the summer when our parents were at work and just the two of us were home.
One morning I sneaked into her room to get something while she was still asleep. The cover was pulled back and although she had on a top, she was naked from the waist down. It was the first time in my life that I saw a pussy. I went to the bathroom as soon as I left her room and jacked off.
After I had finished jacking off I went back and peeped into her room through the key hole in the door. She was awake and rubbing her pussy like there was no tomorrow. I watched until she had an orgasm although I didn't know what it was called at the time. But I did know that she had cum. Since I got up earlier than she did I decided to peek at her the next morning. There she was with that brown pussy hair parted playing with her pussy. She would finger her pussy for a while and then rub her clit. She would do that until she came.
All the while I was peeking through the keyhole jacking off as fast as I could. I watched her masturbate every morning for the entire summer as well as the next summer and the next. I learned a lot watching my sister and had many jack off sessions because of her. She would never let me do anything with her or even talk about anything but I sure had fun watching her. Now all these years later I still get hard thinking of seeing her pussy. I sometimes wonder if she knew I was watching her.