Don’t extend an olive branch, just try to keep some form of communication open, cards and calls for holidays, birthdays, and family events, that sort of thing. And if politics comes up for discussion in any form, take the approach of asking why your brother believes as he does, what events and facts led him to the views that he has, what his thinking process was. Do not contradict him, just try to understand his views. In time, he may rethink things or events may take a hand.
My brother in law is absolutely convinced there are thousands of Nazis marching down the main streets of American every day.
It is kinda hard to prove a negative.
Lol.