Please help - family wedding drama...

So I think my brother isn't fond of my fiancé. My fiance's fam has been wonderful in trying to arrange parties so we can all meet but my brother has been extremely edgey with communication with me. One problem is that we have a disabled brother and very negative father - both of whom he still lives with. I'm not sure if by getting married he feels alone now in dealing with them, but it's certainly his choice to live at home -- he is 43 and (in my opinion) stalling to write an exam that could employ him in meaningful employment for the rest of his life. In turn, he uses this as an reason/excuse not to tend to other responsibilities -- too busy studying and when he's not studying, he's working at the current job he has.

Truth is, I think my brother has never liked my fiancé, (I've never told my fiancé this because he beleives completely otherwise). He has always called him "awkward" or "weird" before we even dated. I am not sure how to handle all the drama that goes with a wedding. It should be the happiest time of my life. My dad has been similar just cause he's old and in general very difficult. Over the years I have bent over backward to help them since my mom died. They have rarely lifted a finger to help me. I feel like voicing how I feel is futile, even though the rest of the world could probably see my point. They will just get defensive.

Best option I feel: Not to involve them in the wedding or in meeting my fiance's family. I have already asked and have been met with much negativity. I feel embarassed that I have to decline on their behalf for any effort my fiance's family makes to connect as a family. I kind of wish they would stop trying in a way. I don't know how to have that conversation.

If you have any advice please share. Thanks for reading.