["My father and brother are in a serious conflict with each other right now, as my father has complained about the way my brother raises his son. Obviously it's a really stressful, tenuous situation and I have no idea who's side to take, and I'm worried it will lead to them not wanting to keep in touch anymore."]
Family conflict is always hard.  Maybe you don't need to take a side and try to work for peace.
My father and brother are in a serious conflict with each other right now, as my father has complained about the way my brother raises his son. Obviously it's a really stressful, tenuous situation and I have no idea who's side to take, and I'm worried it will lead to them not wanting to keep in touch anymore.