I (27F) have a cousin, we’ll call her D (33F) who I always grew up super close with. We were always more like sisters than cousins! Well when I was a teenager and she was an adult, some of the adult men (ranging 20-35) she “dated” (I’m using that loosely because it was mainly just hooking up) would also “date” me. (Keep this in mind for later) So fast forward to adulthood, I thought we were past “dating” the same people because as an adult I realized it wasn’t right to share people with your cousin. So anywho, I had someone that I was dating DW (32ish M) but it didn’t work out. Later down the road I find out they were in communication. I told her the nature of me and his past relationship thinking she would accept and and stop dating him. She didn’t. D continued to date him knowing I had messages that I showed her that proved that at one point he was in love with me. D kept lying saying they were “just friends” even though he already admitted it to me. My whole family (sisters, aunts, ect) told me I was overreacting and if I wasn’t with him anymore then it shouldn’t matter. She also tried to use the fact that when I was a teenager some of the grown men she was dealing with was also sleeping with me. I was a teenager, they were adults, I was a victim! I then cut all communication with my family. Fast forward a year or so later and she apologizes and makes it seem like she doesn’t talk to the guy anymore. We make up and start hanging out again like we used to. Then almost a year later after making up, DWs friend accidentally and unknowing of the previous situation, told me that D and DW were in fact still dating. When I confronted D and my family about it they all said I was still overreacting. Mind you my family was lying telling me D was at different places when she was really with DW. They all knew D was still dealing with him and they lied to my face to protect the relationship between D and DW and D and I. I flipped out and told them they were are liars and untrustworthy. I haven’t spoken a word to any of them since June. AITA? Did I overreact? Or should cousins not date each others exes?