My ex’s brother

My ex and I broke up almost 2 years ago. He has a lot of drinking and drug problems, never works, always blames all his problems on any one he can and has been in 4 serious relationships since we broke up. He constantly accused me of cheating while we were together and I never knew why. I had never done anything unfaithful and was always loyal to him but no matter what he was constantly accusing me of cheating on him. I’ve been single for the whole time we’ve been separated but dated someone shortly for 2 months and it didn’t work out. One person he always accused me of cheating with was his step brother but I never had any idea why?!? In October I was drunk and got in a fight with my baby daddy so I called his step brother out of spite but we actually had a pretty nice conversation for a little over 2 hours and texted some after. Then I knew it was clear that he liked (wanted to bang?) me. I woke up the next morning feeling so embarrassed. We haven’t talked since then but then I have been thinking about it a lot the past couple of days and the more I think about it the more it turns me on. Then out of the blue he texted me and we talked more than I’ve ever talked to him. He will occasionally help me with car problems since I have an old car and he’s a mechanic and it’s a lot cheaper to just pay him to fix it but he’s never acted like he was interested in me. He invited me and my daughter over for Christmas but we’ve been sexting all weekend. I have so many mixed feelings about it because it feels so wrong but that’s the part that turns me on. I told one of my close friends and usually she’s a prude about this kind of stuff so her response was a surprise. She told me since I’ve been accused of it for so long I might as well do it if I want it. My ex and his step brother aren’t close at all and only tolerate each other because their parents are married so it’s not like I’d be ruining their relationship. I don’t know it’s obvious that he wants me so I think I’m going to do it. Has anyone else been in this kind of situation?