Zebra Finch Housing Problems HELP!!?

Ok, so I have A breeding pair of Zebras, who recently hatched 3 babies, two males and a female. they have reached maturity, and I want to avoid inbreeding. I have one spare cage of reasonable size and am willing to buy more birds, to keep them in pairs. I have started a "Remove all fertile eggs from the nest" policy, and i can do that for the new birds as well. Reply Soon!!!! Thanks for your help!!