So my fiance's brother is actually just insane, rude, degrading, and racist. He is completely unlike everyone in his family so I honestly don't understand where he came from or how he got like this. So early on in my relationship, I was friendly with his brother and we would even hang out together, I just kept thinking "This is going to be my family so I need to make it work". So our entire relationship he has always been degrading towards me, calling me stupid, saying his brother is whipped, saying that I boss him around and abuse him ( Which I 100% do not abuse him), and saying my college major amounts to nothing. I have always been sassy back and just brushed it off but it did hurt me. His parents never say anything when all of this happens and have stayed out of most of it using the excuse that he is an adult and can make his own choices. So last summer I had a huge blow up with him, he was yelling at me and cursing at me, telling me I was an idiot. It had all started because he had said something incredibly racist to my best friend about her Hispanic boyfriend that upset her and had her crying. He was yelling at her, me, my mom, and my fiance who were just trying to make him stop.
So we have never resolved the issue and me and my fiance and I just kept our distance from him. My fiance's parents know how much I dislike his brother and how uncomfortable I am around him. So me, my fiance, and our moms were all talking about the wedding and my fiance's mom said "You should start getting your groomsmen together: you have your 2 brothers, and then 3 friends" So obviously she intends that his psycho brother will be a groomsman. We didn't say anything in the moment because we didn't want to have the discussion in front of my mom. Honestly at this point I don't even want him there because I am worried he will get drunk and cause a large scene. Does anyone have any advice on what we should do?
We have tried calling the brother to talk about it with him alone but he won't answer the phone, my fiance's mom keeps bringing up the idea that his brother will be a groomsman and I honestly don't even know how to go about the situation. She event went to the extent of talking to the two brothers about being part of our wedding without us even knowing. Please give some advice everyone!!