Hi!
I am very sorry for your loss.
I would strongly recommend to let your boys live alongside for a few weeks so they can make friends through the bars and your chance of acceptance is much improved. In order to end up with working stable adult boar trio, they have to all
want to be together and the newbie has to be invited in by the two others. It is not something that you can force - the more you push your boys to get on to suit your own wishes, the more likely things are going to fail.
Keep in mind that more piggy trios fail than work out at whichever age or cominbation; older boars over 4-5 years excepted, as their testosterone has fizzled out and the comfort companionship becomes more important in their old age. Younger adults are still on the tricky side unless their personalities really balance and there is a base of mutual liking as well as the right mix of dominance/ambition and submission. But I would never count on it, whatever it says on paper - I have seen to many theoretically perfect matches founder very quickly as you can never predict the interpersonal dynamics when the piggies actually meet. We can give you only trends, based on experience. As in any pairing you do at home, you need to have a plan B at the ready if things don't go to plan.
Please separate straight away if the top boar of the pair is feeling stressed and starts to turn on his mate and immediately stop any bonding attempt; it is never going to work out if that happens! If you don't, you can end up with three single boars if your couple won't make up again. We have seen this happen often enough - with adult boars and not just with babies or teenagers, too.
Bonding and Interaction: Illustrated social behaviours and bonding dynamics
PS: You have obviously never tried to bond older sows...