Starting at about 8 and going to 12 years
We lived a regular family life. My brother was two years older than I and my sister two years younger. When my brother and I were young, we took baths together and as we got old enough Mom would let us alone and we could play and see or Dad would just yell to make sure we were ok. The farthest back I can remember is maybe 6. We would be in the bath and facing each other. I don't know who was the first to notice that our weenies would get hard. Then we would play in the tub with out feet to the other's weenies. It was my brother who showed his off and I just followed. I don't remember the building up slowly; I just remember it happening. We would play with each other under the water. It felt really good.
At this time my brother and I were still sleeping together in one bed. The room was too small for two twin beds, but one bed a little larger was just fine. My brother and I fought as usual and competed as usual, but we were also kind to each other. I think this was when I was 7 and he was 9 he started rubbing himself through his shorts. I would wake up in the morning especially on the weekends and I was hard and my brother was rubbing his.
One day I just reached over and rubbed it for him. He lay back and relaxed. This went on for awhile. He would get hard and I would rub it for him through his underwear. After awhile he would get really going and would reach what I know now as a climax. Shortly after he was having a climax in the middle of it he would reach over and rub me. This only encouraged me more. It felt really good. This really didn't happen that much but enough. When we would go camping it was fun because Mom and Dad would zip our bags together and they would zip theirs and my sister would sleep with them. She was on the outside next to Mom and Dad was on the other outside next to her.
Things changed when my brother got hurt on his bike. He was laid up and we all took care of him for about a month. During this time (and he was about 10 now) he would ask me to rub him. I would be standing next to the bed and would rub him. He would reach out with his hand in my pants and rub me. It really felt good. At this time stuff started coming out of him as he reached a climax.
Again, this was not a constant. I would rub him just a few times a year. When he was between 12 and 13 he wanted me to rub him more and he would rub me at the same time. We learned how to reach a climax at the same time. By now we long since knew about sex and girls and masterbation. We didn't talk about it; we just took care of each other.
Now we were taking out shorts off at night hoping not to get caught. We would play with each other's penis and testicles. When I would play with him he would cum and for some reason I liked him cumming in my hand. I would rub him with it after he came and sometimes I would rub myself. About this time Dad did an addition, and we got a bigger room with out own beds. We still managed to sneak in bed together and shortly we were rubbing our penises together. He would cum and I started to cum. It was about this time that he got into girls. Sometimes he would come over to me and just play with me until I climaxed in his hand and he would say, 'This is payback for you.'
Once we both were into our teens, it stopped. I like seeing him naked and he likes seeing me, but we are just brothers with families and kids now.