For me it started early on in my relationship with my ex wife. I knew she had dated black guys before me and that she was pretty wild sexully. What started out as a little pillow talk turned into us talking about her sexual past almost every time we fucked and at some point I asked about the biggest cock she had ever had and who it was. It was her ex Jeff and she said he was about 11 inches and as thick as a beer bottle. The thought of her being able to take that big of a cock was such a turn on and I brought it up often.
Fast forward 4 years and we had been married for almost 3 years and had a baby. I was working 3rd shift and one night I got off early, around 3 in the morning and she wasn't home. About 20 minutes later she came home wearing a Jean skirt with fishnet hose and knee hi boots on. She was buzzed and said she was out with a girlfriend of hers, which just didn't seem right. I started questioning her and that turned into a fight that went on for about a hour. Then she just blurted yelled that she had been fucking Jeff for 4 months and that she got fucked by him all night! I was pissed and I was hurt, but I was also rock hard. I grabbed her, spun her around, bent her over the kitchen table, yanked her skirt up over her ass, and pulled my cock out. Her pussy was red and swollen, it looked destroyed. I buried my cock inside her and it felt so sloppy and loose, it felt fucking amazing. I was pounding her asking her how she could do this to me one second and the next I was asking if he used a condom, which I knew she hated. She said no and he came in my pussy twice and once in my ass. As she was saying it I came so fucking hard.
Shortly after that we became swingers, then we had a hotwife relationship, and then an open marriage. 8 years later we divorced due to things not related to sex or our lifestyle. I met my current girlfriend around the same time at a swingers party and we have had a Daddy Dom/Little Slut relationship for the last 7 years, but recently we have started to talk about and fantasize about exploring some cuckold fun.