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.
Yeah, you're right. It's kind of complicated, but I definitely shouldn't try to pick sides. I just want everyone to get along, but it's not that simple. It's like I can't figure out if I try to make peace, whether that will make things more complicated or not, and whether I should just stay out of it. Time will tell.
It is rarely easy to know the right thing to do in these sorts of situations.  This might be a situation that calls for some professional help.