Welcome to Binky Bunny!
Before rabbits are bonded, the first step is always to have both (or all) spayed and neutered. Except in the case of very young bunnies (3-4 months old or less) unneutered males should not be housed together. George is certainly old enough to be neutered and Marvin may be too, or it may be another few weeks for him. If his testicles have descended, then he is ready to be neutered. Since Marvin is approaching his “puberty”, which means the hormones will be in full force, it’s possible that he and George might start scuffling or even fighting, so you need to watch for that. You may need to separate them if one or both starts showing signs of aggression, if you don’t go ahead and separate them now Things can sometimes change very quickly with rabbits, when hormones are involved.
If you are adopting the female from a rescue or shelter, they normally spay them before the adoption. Most females are ready to be spayed around 5 months, some vets prefer to wait until 6 months. It would probably be best to try to schedule the neuters and spay (if the rescue doesn’t do that) for the same time, or as close as you can get. After their surgeries, wait about a month to start the bonding process. That would give the female time to completely heal and time for all the hormones to be flushed out of the males.