In addition to physical maturity, it's also important to consider the social maturity of your rabbits. Rabbits are territorial animals, and introducing a new rabbit into the environment can be stressful. It's best to introduce rabbits gradually and in a neutral territory to avoid any potential aggression.
If you're planning on breeding your rabbits, it's a good idea to do some research on the breed and the best practices for breeding. You may also want to consult with a veterinarian to ensure that your rabbits are healthy and ready to breed.