Mother nature knows what she's doing. She needs to be in a cage by herself and in time if there are more babies she will have them. A male mouse will eat any babies that are born in the same cage as him. Rabbits the same. Wait a while and see what happens. You can't rush it, it will happen in its own time. Course there is always the possibility there was only one baby, unusual for a rodent but anything is possible
he is your friend and protector, he will love you unconditionally, you owe it to him to be worthy of such devotion