Welcome to the forum, you'll get tons of great advice and information here. As has been said before, a trio of boys has a high fall out rate, and it's mostly down to their personalities rather than what you do. That said, even compatible boys may fall out if they don't have space and their own stuff. The 4-14 months are the most likely to be when you find out. Make sure you have a plan so that if they do fall out, you can intervene quickly -NOT with bare hands though, as you can get a nasty bite if you get in the way of a full on fight.
I have 3 boars, similar to yours, one is slightly younger but all from the same herd. They are about 18 months now, so hopefully they've made it through (although I still have plan b). They have had their moments, and I have popped in a divider on a couple of occasions when tensions were running high, which gave them time to settle down, but they've never got to a full fight. If that happens, it's pretty much game over.
My boys have a 5x3 grids c&c with a loft, they had lots of 2 entrance hideys and three bowls, water bottles etc., although I have reduced this in recent months because they all eat together and I know their favourite places to sleep, so removing stuff gives them more runaround space.
I believe that, other than personality, the biggest factor is space, space and more space.
Good luck with your three, I hope it works as well for you as it has for me, but I know I'm in the minority with a 90% fallout rate in the teenage months, so if it doesn't work, you're in good company.
