If you're buying fry or juvies, you'd be better off buying fish from 2 reliable sources since then there will not be any inbreeding. Or just get the male from a different source. The only ideal situation that you'd buy from one reliable source is if you bought wild frontosa.
This is of course if you're really looking to breed them. If just for pure enjoyment and you just want a tank full of beautiful fish, just make sure you start with beautiful stock. You don't want to be raising fronts for a few years only to see that their broken bars or mooning never disappeared. (Mpimbwe fronts will sometimes have slight mooning though which is only acceptable in this variety of frontosa.) If they don't have those bad traits to start with, they won't have them when they get older. So the greater risk of bad offspring is breeding poor quality fish to begin with.
Just my 2 cents. Good luck with your fronts!