This question has been posted many, many times, so if you do a search, you´ll probably find many threads on the subject.
It´s a myth that boars can´t live together. Whether or not they are brothers is not really relevant. Introduction needs to be done right and they need lots of space, but several people here have boars living together.
How big is your cage?
Check out some of the other pages at Cavy Spirit too, there´s some great ideas for cages and all sorts of other guinea pig stuff. I hope that helps.
From the Care Guide: http://guinealynx.info/healthycavy.html
SIZE: Consider providing as large a cage as possible -- at least 4 square feet
per cavy adding 2 square feet per additional cavy or more. A larger cage will
require less frequent cleaning and provide space for play, toys and exercise.
CavyCages.com makes a compelling case for providing an even larger cage
and offers creative, attractive, and affordable ways to do so. Visit
CavyCages.com for plans and designs.
If you don´t know the genetics of your animals you could be risking birth defects regardless of relationship. I believe breeding a mother to a son is inbreeding although breeders might have a different term for it. You might not see genetic defects until the cavy is older. Not all defects are apparent at birth.
Didn´t you say you were trying to find a home for your boars?
Also, curiosity is one thing, but when you say "accidently breeded a mom with a son" it sounds to me like it already has happened.
Incidentally, if you decided to keep the other boar, I´m not sure the 3 pigs could live together, even if the boars were neutered. Others may know better, but it seems to me that two boars with a sow would be asking for trouble, because they´d both be fighting to "win" her -- even if they were neutered.
I agree with Pozone that your cage is quite small, even for just one pig. Don´t even think of keeping two or three pigs in there. And one female with two boars is not a good idea.
Ideally, the two boars would be kept together in a spacious cage. Then, you won´t need surgeries.