Board Thread:Character Discussion/@comment-6739926-20150118091358/@comment-24674051-20150128175847

As to the massive overpopulation, I don't see that as a problem. So far, it has been implied that the Fairies are all female. That's not to say that there aren't male fairies, but they must be extremely rare. And given Blue's authoritarianism regarding relationships, there would be little opportunity for any unwanted pregnancies.

My guess is that the Fairies are Immortal (at least while they are fairies), and are only replaced when one is removed (either by Blue, or by some freak accident). And there are probably special fairies and special rules for when a new fairy is born. Tink was stripped of her immortatility while she was a non-fairy, and hence she chose to stay in Neverland.