This happens maybe once a month
Before my brother went off to college I noticed he would masturbate a lot. I would always catch glimpses of him with his hands in his pants while looking at his computer. Well one time he was masturbating and we were home alone. He decided to go into the bathroom. I knew he would be jerking off so I decided to get close to the door. To my surprise our bathroom has a little crack down the side and I could see his face and body above the waist. I was getting turned on by what I saw. My brother Carson was jerking off.
I don't know why but I was so hard. I am straight but for some reason I couldn't stop watching. The thing that got to me was his facial expressions. He looked angry with a grimace on his face then he was looking at the ceiling and his eyes rolled back into his head sort of. He had a look of pure pleasure on his face that is extremely hard to describe. I came pretty much right there. I didn't even have to touch myself too much.
He is back from college for the summer and I try to catch him sometimes. It's hard because my sisters room is right across the hall from the bathroom. I also think he is starting to catch on. Oh well I still get off thinking about the experience I had. I hope this doesn't sound to weird.