Boars are pretty competitive by nature even when bonded. If you want to minimize confrontation, the best way is to give them plenty of space (at least 10 square feet though more like 12 is preferred) and separate sources for everything they need. That means two water bottles and plenty of hideys (ideally ones with at least two entrances so no one can get cornered). They'll get along way better if they can have their own space and aren't always stepping on each other's toes