He never did know.
I had learned how to jerk off by accident one day while my older cousin who was in the army was staying with us for a few weeks.
As a joke I was going to hide in the bedroom closet where he was staying then jump out to scare him. He was coming home and I ran upstairs to hide peeking through the closet door louvers.
John came upstairs as usual but I did not know the first thing he would do was strip naked. I started to quiver as I stood peeking at him now completely nude. I had never seen another cock before and his looked huge to me. Then he sat down on the edge of the bed and grabbed a bottle of lotion. I was so shocked to see him start putting it all over his growing cock. I had no idea what was happening.
He started stroking his cock and I knew it was something that must be good due to his body movements. He stroked away for what felt like forever and then what a shock to me when I saw this white fluid squirt onto the floor as his body jerked back and forth with his head bobbing up and down. He looked so odd I thought. I remember thinking how quiet he was aside from the swishing noise from his hand stroking his huge cock.
John then took some tissue and wiped his cum off the wooden floor. He pulled on his pants and left the room and into the bathroom. I flew out of the room and into mine. I just had to try it. I quietly went into the hall closet and grabbed some of my moms lotion. I locked my door and I tried it myself. Wow what a feeling! Now I knew why he did it and it felt so dirty I remember like I should not be doing it.
Then the feeling of orgasm started to take over and I kept going until it felt so fantastic! I could not believe how great this feeling was. Once I stopped I realized that my cock felt like it was squirting something but nothing came out.
It was only about six months later that I did start ejaculating and to my shock.