This really happened!
One day when I was about 12, Scott 11 and Joe 13 (not their real names) invited me to Joe's basement. They explained to me that they had a game where you fantasize about one of the older girls on the street while getting off. Then they showed me how. Scott put his erection into the fly on Joe's underwear and worked away. After a little effort, he announced that he shot out a quart of sperm. (he had no hair yet but could already ejaculate).
Then, it was my turn to try. Joe put his erection into my fly and asked me to put it next to mine. His penis looked pretty large compared to mine and Scott's. When I moved it next to mine, I was about the same length, Joe just was wider. He started to work away for a few minutes. I was feeling ok too. Joe then let out a small load and was happy. Then I entered Scott's fly and let my penis ride in motion alongside his. All this with no hands! A nice little blast from my 12-year-old penis and I was happy too. We did this for about a year and then Joe moved away.