are they incubating the eggs properly?
Normally the response I get is Yes to both.. If you do have a male/female pair and they are sitting on the eggs well then they could be a bit young to breed. Of so, I’d remove the nest for 2 months then let them try again. You could also easily have an infertile bird, or if they are a brother/sister pair the chicks may be dying before they hatch, a common problem with inbreeding. The solution here is to get different mates for them.
