The first adult penis I ever saw was my dad's while we were changing to go into my uncle's pool. The second one, was a neighbor who seduced me. He showed me a deck of cards that had naked women on them and I got a hard-on instantly. When he saw my reaction, he started rubbing it and then pulled my pants down. I was 13 at the time. He started sucking me and it felt really good. Then he pulled down his pants and he had a HUGE cock. At least 8" long. He kept trying to get me to deepthroat him and then when he was really hard, he bent me over. He pulled out some vaseline and lubed my tight ass, starting pushing his huge cock in me filling me up. It was incredible. It felt wrong but didn't hurt that much I was so hard and desperately wanted to cum. He filled my ass with cum before too long and then he finished me off by masturbating me and letting me cum in his mouth.
Since he was my neighbor, he would give me odd jobs around his house and then invite me in for a cool drink and eventually, fuck my ass and teach me how to suck his cock. (I never learned how to deepthroat him, although I really wanted to). This went on for about two years until I ran away from home. I found out later that he seduced my younger brother and fucked and sucked him regularly too.
When my brother and I got together years later, we talked about our first experience with him. We both were hard as steel at that point and so we both started masturbating in front of each other, recalling this guy's huge cock and the way he would fill us with his hot cum. Before long, I moved closer to him, got on my knees and started sucking my brother like we used to so many years before. (We were experimenting with each other before we were seduced by our neighbor). Then my brother offered his rarely-fucked ass to me for me to fill with my cum "just like the good ole' days".
It's nice to have somewhere to finally let all this out.