Why does an ex-boyfriend that is married want to sleep with his exgirlfriend?

Sounds like there is more going on here than sleeping around. May be emotional or mental problems there. Maybe because of that he needs the extra attention or has sex addiction or is a sociopath. If you happen to be "the girlfriend," my advice is for you to get away from this guy. Even if you love him. It will be tough at first, but trust me, in the future, you'll never regret it. I was thinking the exact same thing. He also uses drugs so nothing would surprise me if he has multiple personalities or something. Excitement? Maybe this married woman gives him things for his services? Maybe she does things the g/f wont? Maybe he has an issue with older women? Maybe he enjoys the attention these married women give him. Sex without committment?