My friend had six younger sisters
After my sophomore year in high school, I spent a lot of time at a friend's house. His older brother was in Vietnam at the time so he had a room in the basement, with a combination shower and lavatory. He also had a collection of nudist magazines, featuring young teen girls. One looked incredibly like his fourteen-year-old sister, who I knew took showers in that basement lav.
There were pictures of young girls showering in that mag, and I would take the magazine in that room whenever I got the chance, soap up and jack off to the thought that my buddy's sister was in there with me.
I'm sure that she knew I had the hots for her, but she was only fourteen (in numbers only), and would leave her towel (and panties) accidentally during that summer.
Was she using me for her fantasies?, probably. Was I pissed? hell, no. Where's that time machine when you could really use it!?