Well not quite an older sister, but for a couple of years my mother & I lived with her friend and her daughter who is 1yr younger than me, we were young. But her mother used to walk around the house naked sometimes, even when I was around and I would get an erection, anyhow the daughter (Denise)...

Well I would masturbate girls when I was young and even lost my virginity at age 12.5, I personally didn't masturbate myself until about a year later, after we moved and I was no longer having fun with my girls. I would go to the bathroom and get an erection and one time I felt the urge to stroke it...