mypockets
I had a similar problem to you a couple of years back.(In the October)
Brief history:
My DD and I got two 1yo brothers. Their outdoor house is my DC old wooden Playhouse, so lots of room, hay, hidey spaces.
Heater for winter, fan for summer.
Until they had to come indoors for Guy Fawkes....... I'd bought a 4'x2' cage (the biggest one I could find). They were in the dining room.
And I made a huge mistake of giving them a load of coriander (they love parsley, coriander turned them bad)
The smaller one went for the bigger boar. Got his teeth onto his back. There was no face-off or growling, it was All Out War.
So, by night , we seperated them. A metal grid to give each 2'x2' but this was only their night winter cage.
Every morning they went out to the Pighouse. I made sure the food and water was well apart.
They were fine in their run, in their Pighouse. Not in the indoor cage.
Next winter, I didn't divide, but I filled it with hay and gave each a box. I put them in the small bedroom with a duvet over the top to insulate against draughts and noise. They were fine. I could hear them at night.
We now have a young boar (the little pig died) and I gave them a bigger indoor run. Piglet tries to bonk the older one but minimal squabbles.
If you are unable to re-introduce them (try everything to make sure they have enough room. Maybe try everything neutral again. Boxes with open doors so one can't trap the other) then if they have to side-by-side it;s not the end of the world.
My boars (GP1 and GP2 were brothers) GP1 and GP3 were boar matched when GP3 was 6 weeks old. They don't cuddle together.
They might sit in the Haybox but not snuggled up,
Or one will be in there, the other in one of their houses (I have hay all over the floor of the Pighouse at the moment)
If they can see each other to chat, that's better than being alone.
Neutering two boars to live together won't change them.
Neutering two boars to pair with sows is lovely. But you have no guarentee <span class="italic">they'll</span> get on. There's a risk in surgery. And you are doubling you're food/cleaning.
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When you say 'massive' cage, how big?
(As an example, my fur babies have an indoor run that is about 5'x3' with an extra bit into the bay window - it's flexible panels. It's a nice size for my boys and gives them twice the area of their nark inducing space)
C&C cages might be worth a look.
I got some cube shelves from Costco which are similar (in case I ever need to rustle up a cage <span class="line-through">or someone leaves a box of guinea-pigs on my door step</span> )