I read a post a while back on another site about a girl seeing her brother and male cousins through a hole in the shower.
This prompted me to tell my story. I have one older and one younger sister. I took over the large bedroom when I got a weight set at twelve. I eventually found a plumbing access in my closet for the shower on the other side of the wall. I removed the cover and found I could see the inside of the tub through a gap between the tiles and the shower faucet handle.
I soon began watching my sisters (10 and 14) through the hole. I could see their legs from mid-thigh down when they showered. When they bathed, I got glimpses of their bodies when they sat down in the water and when they came back up.
I quickly lost interest in my younger sister, but was totally turned on by my older. Over the next year, I got to see some of her pretty frequently, and to be honest masturbated while I peeked.
Eventually I wanted some other stimulation and hit on a plan. I got rid of the weight set and allowed my older sibling into arguing to get her room back. It was originally hers.
I made sure the cover was on the access, but that the panel was visible. I began to loosen the screws more and more over the next couple of weeks until one corner eventually 'slipped' loose.
Once she knew it was there, and I found she had put the cover back on, I would put the screwheads in a certain angle so I would know if she was taking it off. She was.
I got turned on everytime I showered knowing she was peeking. At first I was afraid to show anything and would just stand and masturbate knowing she was watching my legs in the shower.
Eventually, I would wait till hard (not long with the anticipation), then drop the soap and kneel to pick it up. Only a quick glance at first. I was turned on, and really embarrassed at the same time.
I finally got around to putting water in somewhat shallow, and bathing with my genitals exposed. I was fully hard the whole time. The next time, I actually masturbated in full view of her.
I don't know how often she watched over the years, but I eventually got tired of the show. But I still masturbated over thoughts of her sometimes.
Now, as married adults, I still fantasise about that. Recently, I even brought up the panel to her, and she admitted that she watched me.
No way can anything ever happen, but now I am totally obsessed about her.