When I was 13, my mother got remarried to a guy with a son that was exactly my age (we were born just two days apart). When they first moved in with us, it was really weird, and we barely spoke. After a couple of months we became friendly, and by the time our 14th birthday came along we were pretty much best friends.
A couple of weeks after our birthday, we were both watching TV in the family room. I looked over at my step-brother, whose name is Will, and I saw something odd in his pants...he had a boner! This was the first time I had ever seen a boner even through pants so I was kind of excited. A couple of days later, I saw he had a boner again when we were both hanging out in his room. I was starting to really enjoy seeing him hard, and I was getting more used to the sight. After a couple of more days, I saw him hard again. We were in the family room watching tv like the first time I saw him.
I thought it to be fun to be smart and tease him so I said: 'Hey, Willy, you enjoying the show?' I pointed at his crotch as I said that. He was smart too and said: 'No, but you are. 'Then he quickly pulled down the front of his pajama pants to show me his big boner. I yelled 'Ew' as he laughed. We continued to sit there, and I continued to monitor his boner. After a couple of minutes I noticed that he began to rub his penis through his pants, and then he put his hand inside his pants. I was fascinated as I watched him work his dick under the thin fabric. He stopped and I marvelled at his tent. Then he unbuttoned the pajama pants and then his boxers. He then slipped his hand in and pulled out his six inch circumcised penis.
He began stroking with his right hand, still just watching the TV, not me. After a couple of minutes he turned his head to me and asked me to change the channel because I had the remote and he didn't like the show that was coming on next. I obliged, stunned that he could just talk to me as he was jerking. Another minute later he asked me if I had a tissue. I, like a zombie, grabbed and passed him a tissue. He thanked me as he stripped off his shirt to reveal his sexy abs. He started stroking faster and all of a sudden he came with a sexy grunt and loads of semen covered his chest. He started to clean himself up and asked for another tissue because one wasn't enough. He stuffed his semi-erect penis back in his pants and rebuttoned when he was clean. Then he got up to flush the semen covered tissues and to wash his hands. When he came back he acted like normal. He just put his shirt back on and asked when are parents were coming home. (Luckily they were out of the house for this episode).
That night, when I was brushing my teeth, he came into the bathroom and took a piss right in front of me. By the end of the piss he was hard, but he just put it back in his pants and said good night as he left.
All of this started years of exhibitionism (for him). He would always use the toilet when I was in the bathroom brushing my teeth or brushing my hair or putting on makeup. At first I was always silent during this, but then we began talking as he peed. I think he would shake his dick a little extra at the end for my viewing pleasure. I didn't really mind the pee (I actually loved the sound of his stream hitting the water), but when he first started pooping in my presence I was a little disturbed. Eventually I got used to that too though. I was actually really turned on when he once jacked off while on the toilet.
Every morning before school (which was too early for our parents to be up), he would always shower while I was getting ready in the same bathroom. More than that, he would jack off in the shower, sometimes using my conditioner as lube. I would always watch him in the mirror, and I think that he sometimes splashed the glass door to make sure the condensation didn't obstruct my view. After his shower he would dry off in front of me and then shave naked right next to me.
Whenever we were home alone, which was quite often because of our parents' work schedules, he would not bother to leave the door closed when he went to the bathroom and would jack off all over the house. He would jack off as we chatted, watched TV, listened to music, did homework, and ate. Once he actually accidently came on his food and I laughed as he ate it anyway. He would even jack off completely naked while watching porn when I came to talk to him about something.
I never exposed myself to him, and he never asked me to. Once or twice I did rub myself in front of him but I just put my hand down my pants, not allowing him to see much of anything.
I watched him cum probably two or three times a day everyday (sometimes during the summer it'd be five to seven times a day) from when we were 14 in middle school until we went off to college.