HUGE fight over my boyfriends brother

My bfs brother is a jerk. Always has been. The first incident was When we were all drinking and I made a joke in reference to a funny story He told and everybody started laughing and he felt like everyone was laughing at him and he got upset at me for it, It was literally the first day I met him. Hes always had an issue with me, Last year I talked to his gf about it and she said she has even addressed the issue with him as shes also noticed how he’s rude to me for no reason and the only explanation for his actions are “I’m stupid”, meaning me not himself. So she just assumed that he was jealous of me as his brother & him are very close and she thought maybe he’s just jealous that he doesn’t have his brother to himself anymore. last year things weren’t that good between my bfs brother and I as he would just be sarcastic with me a lot for no reason or some days he would be really cool with me and some days he would be in a bad mood. It started bothering me and I started taking things personal because I would notice he wouldn’t be this way with any of our other friends, he treated them all with respect I’m the only one he seemed to pick on. The breaking point was last year when we were at his house for a bbq and I was putting a tampon in and accidentally flushed the applicator clogging up his toilet. He didn’t know I was the one who did it but I had told my bf and my bf ended up fishing it out. His brother saw him messing with the toilet and ended up helping him unclog it. When his brother saw it was a tampon applicator that clogged his toilet he was furious. He grabbed it and walked around the house asking all the girls (there were three of us there and he had gloves on btw) whose tampon it was. Two of the girls said they used pads and I said I used tampons but it wasn’t me( I was too embarrassed to admit it was me) he ended up blowing up on me saying it must have been me and that I shouldn’t be flushing those down the toilet this and that etc. I was HUMILIATED!! My boyfriend didn’t step in until after the fact, he pulled him outside and told him something for talking to me that way. But I was livid that my bf didn’t intervene while it was happening. He let him tell me shit and embarrass me in front of everyone! His brother is just an obnoxious jerk and his family never tells him anything they let him get away with his behavior because their scared of him. HE HAS ALWAYS GOTTEN To behave this way because nobody has ever told him to Knock it off! Anyways he ended up apologizing after talking to my bf and we moved forward. Since than things have been okay but he will still be in a mood sometimes, he hasn’t really disrespected me since but I dread going over because I’m always on edge never knowing if his sarcastic comments are coming or not. Well last night we were at his house having dinner and his gf asked if I wanted to try some of her wine and she handed me her glass, I grabbed it to smell it because I wanted to see if it smelled bitter or not and he flipped out on both of us. Telling her to not be giving me the damn glass that there’s covid going around and that I shouldn’t be trying to drink out of her glass, I can get my own glass “come on you know I don’t like that shit!” And just kept scolding us. I was embarrassed and upset and almost started crying because WHY does he talk to me this way! It upsets me! I’ve never shown him anything but respect. I could never imagine doing the things he’s done to me to him. And if your so fuckin concerned about covid how come during this whole time your still having people over still trying to bbq every fuckin day and always be around everyone! He picks and chooses when things are right and when their not. His gf and I just stayed quiet and that was that. My bf wasn’t in the Room so he didn’t hear. On the way home my bf was talking about when we were eating dinner and how his brothers presence makes things awkward. I had thought the same thing also, his mom was there and we were all eating and it was like nothing in particular happened (this was before the wine incident) it’s just an awkward vibe when he’s around sometimes because you never know what kind of behavior he’s going to be on and it’s sad that even his own mother doesn’t know how to act around him. So I agreed and than I just started crying and told him how he had yelled at us about the whole wine issue. I told Him I was tired of his up and down personality and how it affects me! My bf was just quiet while I talked and when I was done he apologized but that was all, so instantly I became upset and defensive because I felt like this was going to be another situation where he didn’t defend me so I started raising my voice at him and then it just escalated from there because he got mad I raised my voice and I pretty much told him that I felt and disrespected and I was sick of feeling this way every time I’m around his brother and I’m sick of him never really doing anything about it and I’m sick of everyone just brushing it off as well ” that’s just how he is.” How come from the beginning after the first incident you never sat him down and let him know to never speak to me that way again. It’s gone on for so long he’s comfortable with disrespecting me. He expects so much respect but never gives it. Anyways it was a huge fight I was bawling my eyes out and ended up sleeping on the couch all night. Well this morning my bf comes to me and apologizes and tells me how much he loves me and that he was going to tell his brother something he just wanted to tell him something in person not through text. I was still a bit upset about it because yesterday I was clearly very upset over it and I felt like he should’ve acted on it right then and there not a day later. there have been two incidents where my bf felt disrespected by my sister and instantly in that moment I shut it down, I would never let my SO feel uncomfortable or disrespected, I just wanted the same from him. Anyways if you’ve gotten this far thank you. I guess what I want to know is do I have a right to get upset at my boyfriend and also should I just cut his brother out of my life completely for now. I feel bad because that is my bfs brother and they are a very close family and I don’t want to keep my bf from his family but also I cannot deal with having a nervous stomach every time I go over or feeling like I need to kiss his brothers ass to have him be nice to me for the time that I’m there. I just want to be there and enjoy myself, I am always on edge because I never know if I’m going to say the wrong thing that’s going to upset him or if he’s going to Be in a bad mood and just want to take things out on me. can you guys please help me, is it wrong to cut off my bfs family I just don’t know what to do. He’s good to my bf and he’s always there for him and has done things for us and some days he’s really polite to me but than some days he’s not. I know a lot of the things he’s done for us is only because he cares about his brother but sometimes I wish he would care about me and respect me also the way that my boyfriend respects and cares about his brothers gf. I guess last night I just didn’t feel defended or protected. I did go through my bfs phone this morning while he was in the shower and did see he had ended up texting his brother this long message. His brother basically texted back saying when he got mad about the wine it was directed towards his gf not me and that he wasn’t sorry and wasn’t going to keep explaining himself. By the way we are all in our 30s so I just don’t feel like this behavior is acceptable. Also I DID insist on not going over because the whole social distancing shit but his brother would’ve gotten upset if we would’ve bailed on dinner because his mom had came in from out of state to visit so we had to go. Ugh it’s all a mess!