DB and I never got along as kids, and we have absolutely nothing in common as adults. He's always been neurotic and ridiculously sanctimonious. He's gone completely hysterical over Covid and has passed the hysteria on to my mother, with the result that both of them are now acting totally irrationally and have been since early last year. I was struggling to justify maintaining any sort of contact with him before this latest nonsense, but this is the final straw. I'm NC with both now because my life is far simpler and more enjoyable without them in it.
People used to say 'you can choose your friends, but you can't choose your family', and while that's essentially true, you can choose to have nothing to do with people who don't enrich your life in any way regardless of the fact they are a relative.