I have a trio of boars. I started off with two babies (Moxie aged 5 weeks and Cenci aged 7 weeks when they met) and they became best friends. Then after a few weeks a friend told me about a rescue boar (Meeko) that the local ISPCA inspector had, so I just had to adopt him! I was thinking of getting him neutered to live with my girls but then heard that you shouldn't neuter an old boar, and I think that Meeko might be quite old.
So I kept them living next door to each other for a few weeks and then introduced them in a run on the grass. Meeko is very laid back and Moxie is not very dominant so they were fine but Cenci lunged at Meeko to attack, and my hand got in the way and I got a bad bite! So they continued to live next door, and their next meeting went well. Cenci tries to be dominant but Meeko just ignores him or pushes him outta the way! And Cenci has kinda accepted that Meeko is much bigger and is the boss.
I knew it was risky to try to get them to live together, but once I got to know Meeko and how laid back he was, I had a feeling they'd be friends, especially since Cenci and Moxie were best friends from the moment they met.
So far so good, but Cenci and Moxie are teenagers now, which can cause problems apparently, but they are ok so far. I'm really hoping that Cenci doesn't cause more trouble going through his teenage years, but if he does then he might be the one getting neutered to live with the girls! Moxie and Meeko are very good friends and groom each other and all, so I really think they're not going to fall out, but Cenci could cause trouble with Meeko (though Cenci and Moxie are great friends). Sometimes the boys do rumble at each other or chase each other, but not too often and I think that is normal. They don't fight or argue really, or hump each other. All three do eat together and cuddle up together now, so hopefully it stays that way!
It's pretty risky to house three boars together, but since your older one is quite laid back, that should help. Maybe it'd be a good idea to introduce one baby first, and wait til he has gone through his teenage years, and then get another baby one? I'm no expert but I heard it's bad to have two teenagers at the same time. If it doesn't work out then you might have to seperate them, so beware of that.
I've heard of it working for a few people and also someone on here had 2 sets of 4 boys living together, so it's definitely possible. Make sure they have loads of space though. My three boys have a 3.5' X 1.5' double hutch with a 4' X 3.5' run attached to it, and I'd say that'll be just about big enough once the teenage boys are fully grown. (I never knew boars got so big!)