Yes, I have this situation happen all the time. Everytime there would be a family get together, some 'blow out' would happen, between adult siblings or with the parents and adult siblings, or aunt. There is so much pressure to have the perfect happy extended family, and so many out there are dysfunctional (mine included). You can't 'wish it that way' it doesn't happen. I often wonder, 'why God did I get stuck with this bunch, because I would never knowingly ask for them' yet I know I have two options, to deal with them or not. My relief was to move to the other side of the country, and honestly I don't miss all the drama, none of it. My brother called to tell me the huge blow up that took place over Thanksgiving dinner there with the whole family - and I was thankful I had no part in it, just me and my kids happily spending Thanksgiving together with no extended relatives.
So my answer is move ! :)
If you can't do that right away, just don't include yourself in family functions, keep your distance and that way you won't be lured in to all the drama.....