Leave the country and don't take sides unless you want to lose one side or even possibly both.
Families fighting is an absolute nightmare for the family member(s) who isn't part of the disagreement.
At some point, one side or maybe both sides will drag you into the disagreement to get you to side with them and this is when the problems start. Side A will accuse you of helping side B, Side B will accuse you of being disloyal, hence you fall out with everyone over an argument which has nothing to do with you and you were not involved in.
I seriously feel for your predicament as many families seem to have this problem. I know mine has been a nightmare in the past. It got to the point where I don't really want to know any of them. Throw money and wills into the equation and the problem multiplies infinitely.
My answer is to never forget to send cards at Christmas and Birthdays. Call everyone once a week and stay as far away from them as possible.
My original advice was leave the country, I am English. I live in Thailand. 'Nuff said.
Hope it all calms down and you get out of the line of fire, its an awful position to be in, so my best wishes to you :-)