Even a 5 or 6 year old rabbit could be neutered if you have a good, rabbit savvy vet, who approves the surgery. A vet would do blood tests first to check his liver function and also give him a good overall checkup to make sure that he is healthy.
At some point, almost all rabbits are going to need vet care – for illnesses, injuries or just routine checks. So it is important to have a vet you can count on to give the correct treatments and provide any surgeries needed. It’s best to have one lined up, and not wait until an emergency comes up. Vet care for rabbits is unfortunately not cheap. It’s really not cheap for any animals, but rabbits are considered exotics and their care can be higher, plus most low cost spay/neuter clinics don’t include rabbits.
If your females aren’t spayed, they shouldn’t be together either, if they have reached the age of puberty, which can start at 3 months. Baby bunnies are fine together, but when the hormones come flooding in, there can be attitude, aggression, fighting and injuries. And if they’re not spayed, you can’t even let them be around your unneutered male at all. It only takes a few seconds for pregnancy to occur.