Guardianship when siblings don't agree. What happens?

A few of the siblings are not in agreement w/ my mother's DPOA (it was a riot when they found out about it a few months ago after my mother's TBI) and previously threatened to take me to court (many ugly allegations/threats all when I was 5 months pregnant at the time). Needless to say, it has not been used in any capacity, so there was nothing to contest. We recently were in the process of arranging co-guardianship for both parents, me & my sister, all parties agreed after a long discussion, but then one big-time bully who lives out of state is contesting this. So since he threw a wrench in things, our plans did not move forward and the only people suffering are my parents. Plans need to move forward: placing my father, selling the house, making pre-arrangements. I asked my one brother that I trust to step in and do the co-guardianship with my sister but of course a different sibling is not in agreement with that either. My sister wants to do it solo but I don't trust her since she goes with whatever the bully says (right or wrong). She's the oldest and feels that she's entitled to it. The good brother told everyone that if we can't agree, that he'll go to the courthouse and most likely an independent person steps in?? He doesn't want to do that but it's the only way for things to move forward for the sake of both parents. We don't want a stranger in charge BUT as crazy as it sounds, I may trust a stranger more than the 2 siblings I mentioned earlier. If we agree to just my sister doing it, it saves lots of drama BUT I know wholeheartedly that it's the wrong decision. In the end, we don't agree on multiple issues and she has such animosity towards us that I can't see it working at all unless it's her way only. In NJ, how does this work?? Would other people be interviewed besides us (siblings) to determine who would be the appropriate guardian?? like close family friends? Many people know how much certain siblings have done to help and how others have done nothing except add more drama to a horrible situation. When siblings cannot agree, does it automatically go to an independent court person & if so, do we still have a say in helping to reach certain decisions?? If it does go to a court situation, I'll have to bring up the DPOA and then all hell will break loose. I see things getting worse at a time when we need to come together and make important decisions for our parents.