This happened when my cousin Gary and I were fourteen years old and I was sleeping over at his house.
On Friday night we stayed up late playing video games. At two in the morning we were really tired and just stripped down to our underwear and went to sleep in his bed. I woke up about nine and had my usual morning hardon. I decided to pull my dick out of my underwear and play with it. Gary was still asleep, but he had a hardon too, and I decided to wake him up. He was startled at first to be woken by me, but his hardon didn't go away. I kept playing with my dick while we were talking and told Gary that I usually jerked off every morning. He started to play with his dick too.
Neither one of us could see our dick's because we were still under the covers. We started to talk about porn mags that we had looked at, and Gary said that his parents had some porn movies that we could watch. This meant that we had to get out of bed and go to the family room in the basement. Both of us agreed to take off our underwear and get out of bed at the same time. Neither one of us had seen the other naked before and looked at the others dick for a few seconds. Each was about six inches long and uncut, but Gary's was thicker than mine. Gary's parents were both at work so we went to their room and picked up the movie and headed for the basement.
Because the basement had been flooded a couple of days before, Gary said that we would have to wear rubber boots to get to the family room. We went to the mud room and each of us put on a pair of rubber boots, then went to the family room. The movie was a European gangbang movie and both of us were super hard as soon as we started to watch. We sat down beside each other on the couch and jerked our own dicks.
Gary took his right leg and set it over my left leg. I loved the way that the two rubber boots felt rubbing against each other. After about a minute or so he blew his load all over my stomach. Seeing all of the cum on me, I couldn't hold back any longer and shot my load all over his stomach. As we continued to play with the hoods of our softening dicks the cum dripped onto our rubber boots, and the carpet.
Needless to say, we have had more sleep-overs, and each time we wear our rubber boots.