After all these years I still think about this when I jerk off
When I was ten my parents broke up and my mother remarried a man with three children. For two years I kept my distance from my stepfather because I felt if I treated him like a dad I would be betraying my real dad with whom I spent at least every other weekend. My stepfather never disciplined me but left it to my mother and father.
When I was twelve, I started having small, weak orgasms and emitting just a few drops of clear fluid, but I was very proud of it and showed my ten-year-old step-brother what I could do. Then I asked if he wanted us to try and see if he could do it. He agreed and I pulled down his pants and was masturbating him for a long time. He was loving it but not having an orgasm. When he started to feel real good he got scared and made a loud sound.
His dad walked in in his pyjama bottoms and was shocked when he saw what I was doing. His shocked look turned to a fearsome rage in his face and he came over to me and pulled me over his lap. I was wearing just my underpants, and he pulled them down to my feet, and started to slap my ass. I felt humiliated because his son was watching and also angry that he took this liberty of punishing me when I felt he had no right over me.
He was wearing black satin pyjama bottoms that I can remember very well. I still had a hard on from what I had been doing and as he slapped my cheeks I automatically reacted by pushing my hips forward into his lap. The feeling of the satin rubbing on my hard penis, and the intensity of the humiliation and pain, were getting me harder and bigger than I had ever been, and I started to feel waves of pleasure from it all especially feeling the satin. I began rubbing and pushing my penis into his lap with each spank.
He stopped for a moment and then something changed. He wasn't slapping with such anger and speed anymore, but was carefully, slowly, and rhythmically paddling me with his hand. Enough to sting, especially since my ass was now cherry red, but with not all that much force behind it. Then I felt his dick under the pyjamas getting hard and poking up into my lower belly. I couldn't believe how good it felt and how big he was. From my immature point of view his dick felt like it was monsterous.
He would now push up just a little with his own hips when his hand fell on me, so we were both pushing our hips together at the same time, and our penises were rubbing together even though the pyjama separated us. After a few minutes he made a sound like a loud moan and stopped moving. I felt a warm wetness coming from him through the pyjamas and spreading all over my belly. I knew what was happening but I was shocked at how much juice there was since I had been making so little.
At that very second I felt the best thing I had ever felt till then, and shot a real big load for the first time in my life. It didn't just drip out like before but shot hard and kept shooting and shooting. I felt so exhausted that I stayed there over his lap just lying there panting and panting. We just stayed in that position for a while. I was confused but felt calmed and reassured when he put his hand on my hair, and stroked it.
His son had watched the whole thing and never knew what happened. When he saw that I had relaxed some, and seemed ok, he just stood me up and walked out holding his hand over his wet crotch. I went to the bathroom and took his cum and mine in my hand and examined it really close for a long time. After that, every day I masturbated thinking about him. We never talked about it, and we never did anything like that again, although we were much closer afterwards and did things like wrestling, which was very exciting for me.
Also I tried to look at his dick every chance I got, like walking into the bathroom when he was showering. I know he knew what I was doing because when I would do that he would make sure I got a good look at his dick. He is now divorced from my mother and I have not seen him in three years as he moved away, but we send each other cards for holidays and birthdays.