Hearing about her boyfriends
When I met the girl that I would marry four years later, she was dating a guy that I knew. She and I had some of the same college classes, so we often ate lunch together. As we got friendlier, she would tell me about having sex with the guy that she was dating. I particularly enjoyed hearing about her losing her virginity. When they broke up, I asked her out, but another guy had already asked her.
I would look at her mouth as she ate lunch and think about his cock in it and him comming in her mouth. I would go back to my dorm room and beat off.
Finally, she broke up with him and she actually asked me out before I even knew that they had broken up. She said that she wanted to see if we had a future together before we graduated. We went to a movie and then to her dorm room after. Soon, we were naked and I got on top of her and she guided my virgin cock into her pussy. I came very quickly thinking about the two guys that had cum in her before me.
Most of the time during our 40+ year marriage, I have thought about the guys that came in her before me during foreplay and then I would get hard and we would fuck.
My ex was the same. she loved hearing about all the women i had been with and she would get more turned on and sexual