Make a vet appointment right away, and keep them separated until you find out if at least one of them is spayed/neutered - as bunnies can breed early and often. The vet will also be able to approximate an age for you.

Other than that, you can keep them together all the time, if they're bonded and get along, that's great.

I wouldn't plan on letting them sleep in an outside hutch - many predators are active at night, and rabbits can literally be frightened to death even if the predator cannot manage to get into the hutch.