Hi Rachel.
keeping unneutered Bucks together is very risky even ones who have lived together since birth.All may go well initially, but as soon as the hormones kick in really nasty fights will ensue.
If the Bucks are separated and left unneutered they will become difficult to handle in a lot of cases as they are constantly hyped up!.
It really is in their interest to get the Bucks castrated when they are young and fit then so many more doors are open to you re bonding the bunnies, and they will calm down making them easy to handle.
We have an elderly Buck who is unneutered and it is such a shame as he would love a companion, but it cannot happen.
He is really too old for operations, as he is fragile, and it is sad to see him obviously delighting in sniffing other rabbits through the wire doors of the cage, but not actually being able to snuggle up with one. :?
We considered getting a spayed Doe companion for the old Buck, but he would just drive the Doe mad with his demands, and this is not fair!.
We recently had our gorgeous Dalmatian Rex youngster castrated, and he was all cuddly when he arrived, but once the hormones kicked in we could not get near him as he was manic and spraying everything.
I doubt he was a truly happy bunny either, as he was basically going nuts when he spied any rabbit(or us!!..so I guess guinea pigs could trigger a response too in your boys!) in the distance at the Sanctuary.
We really felt it would not be in his interests to leave him like that, and we now have the option of getting him into a group, or at least bonded with a companion later. Rabbits are social creatures by nature, and it is lovely to see mutual grooming, and frisking as they run together