i dont want to go to my brothers wedding...

Long story short, I dont get along well with my brother or his fiance, and neither does my other brother.
Over the past couple of years there has been multiple occasions that have caused us to basically have a huge family feud. His fiance is insane. And by insane I mean she was more than willing to scream in my father's face about a disagreement they had (of course he stood his ground, but nonetheless). She even went as far as to threaten to take away their first grandchild who my mom has basically raised under her roof... crazy, right?!
Anyway, they've been engaged since they found out they were pregnant and decided to throw a wedding together in less than 2 months. None of us want to go because we dont get along nor do we agree with the wedding. I need some opinions please!