I [27f] have been in a sexual relationship with my married first cousin [34m] for the last 4 years

So I'll try to make this story as short as possible.

A little about me. I'm 27, in law school, and recently broke up with someone I had been dating for the past 3 years. I grew up in prominent family of a smallish town in the south. The cousins on my dad's side of the family (we are a large family and I have 8 aunts and uncles on each side, so 16 in total) are in groups. There's a group of girls my age, then a group of guys with a couple of girls that are in their early to mid thirties right now. I would be lying if I said I hadn't been attracted to this particular cousin my whole life. Growing up he was just an older cousin I barely talked to. The younger group was always playing outside while the older boys always hung out together. So, while we frequently had family get togethers, the two groups rarely mingled, leaving this particular cousin to seem like a cute mysterious older guy, but someone I never formed much of a bond with.