We have two boars, their is the dominator (howard) and the dominated (vince).
We have found having two separate pigloos has helped with the issue as they can sleep away from each other if they so wish and we keep an eye too make sure they dont both stand up and fight each other. if they turn into a ball of fighting then they would need separating. until then it is normal behavior.
so importantly if they BOTH (not just one) stand up before a fight, try and intervene with a towel before they aggress, if they fight too a point where they turn into a ball of fighting, then separate them completely (probs permanently). but two or more boars will always have small fights but if they start bleeding then those wounds will need treating.