I think it is a good idea that you had your boars neutered in any case. If they were to fall out with each other in time to come, then you can just split them up, and put them with a girl each straightaway. If you hadnt neutered them, they would have to be seperate for some weeks from the girls, so they would be quite lonely for a while. You wont have that problem. O0
Or even further in the future - if one of them dies, for example of old age, you can put the remaining one with a sow, as from what I have heard, the older the boar, the more difficult to pair them up with another boar. However if you hadnt neutered your boar, he might at that point be too old to have the operation done (the older the higher the risk), and he might end up spending the rest of his life alone.
So I think you having neutered them is an investment in their future happiness
As for keeping more than one boar in the presence of females... I personally wouldnt risk it. Most males would start arguing over the females, this is only natural. The only cases were I have seen it work out was if one of the boars was really laid back and easygoing, or if there is really LOADS of space. A friend of mine has quite a large setup, and she tried it; for a while it went well, nothing happened apart from the occasional teeth chattering of the males, but most of the time they just kept out of each others way. But in the end they DID fight, and I think it is just not worth the risk. Boars want girls of their own, and I think that should just be accepted like that. I think most of our boyfriends and husbands would agree
So what are your options.
You could either just keep your two boars together, and see how they get on. You can always get two sows to make up two seperate groups once the boys HAVE fallen out. If you are lucky, they might never.
Or you get the sows straight away and have two groups. What I would NOT advise is having the 2 sows together, and the two males in a seperate group - even just the smell of females nearby might start fights between them.
so either keep the situation as it is, or make to sow+boar groups, but I personally do not think anything else would work.