You need to have them neutered asap....some vets will operate at 16 weeks provided both their bits have dropped.
You need to keep a very close eye on them, a fight between two boys can get very nasty, very quickly. You may need to seperate them until after the operation and then try to rebond them once their hormones have settled.
Unfortunately male to male pairs are one of the worst combinations, even when littermates and once they have started to scrap it is unlikely they will ever stop completely.