My (F23) fiancé (M24) wants to make my ex (M26) his best man. I’m not comfortable with that.

I F26, knew my ex BF27, ‘K’, from age 16 to 19. He was my first and only boyfriend until I met my fiancé. I have not had any other relationships than these two and neither has my fiancé. He has a special dislike for my ex, probably because I wasn’t a virgin when we had sex first. <br><br>At age 19 I broke up with K after catching him cheating. My best friend, A 24F and I got revenge on him by sleeping with his best mates. His best mates felt guilty about it and told K about it. He went on to sleep with my best friend A. I was furious and although she was my best friend I stopped seeing her for years. I’ve recently reconnected with my best friend A and she’s now dating K again (and has been for the last 4 years!)<br><br>My fiancé and I got engaged a year ago but as we are still finishing our studies we decided to get married in 2 years. We decided on maid of honours and best men to be our friends L 23M and N 25M. My best friend A is one of my other bridesmaids. My best friend A and my ex K are getting married in 6 months which is about 1.5 years before our own wedding. I had a feeling that my best friend A would invite my ex K to her wedding but I did not want to go, as I don’t want to “spoil” my best friend A’s day.<br><br>K messaged me to catch up and I agreed. I met with him at a coffee shop last week. I asked him if he’d be inviting me to his wedding. He explained that since we’re not friends, he doesn’t want me there. I was ok with this and asked him if he was ok with my best friend A being my bridesmaid. He said he’s ok with it. Then, the conversation turned and we talked about my wedding. I mentioned that our wedding isn’t going to happen for 2 years (I had completely forgotten that we’d already chosen L and N as our best man) and then mentioned L and N. I said something like “yeah we’re going to have L as the best man and N is the other best man”. He laughed and said that’s so special that your husband has two best men. I didn’t bother correcting him, I just said we’re going to make it a special day. Then my ex said “yeah, I thought you’d have me as your best man”. I said haha no. <br><br>The next day my fiancé calls me up and says that we need to talk. I said what’s up but he said he’d rather do it in person. I met with him and he says that K told him that I said I would have him as my best man. I said that’s not true. After a small argument, my fiancé said that he wants K as his best man. He explained that when we talked about wedding stuff we both agreed to make it a special day for both of us and he wanted to do this. I wasn’t comfortable with it and said that I didn’t want K at our wedding. He said that he’s fine with me having his ex at our wedding (she’s one of my bridesmaids). I said I don’t feel comfortable with having K at my wedding. He said that he wanted me to be his best man if we weren’t dating so he wants K as his best man. We are now in an argument as my fiancé is not taking no for an answer.<br><br>What do I do? My best friend A and ex K are getting married in 6 months. My fiancé says that K will choose my best friend A over me and wouldn’t come to my wedding if I don’t say yes. <br><br>TLDR! my fiancé wants my ex to be his best man at our wedding and I’m not comfortable with it.