Same nestlings as reported by TomT at https://canberra.naturemapr.org/Community/Sighting/4186150
The adult male was high in the tree when I noticed a female head appear from the hollow, but with a light beak. I thought initially it was the adult female looking out form the hollow but was confused about the beak. Shortly afterwards the adult female became apparent in the tree and there was now a female and a male head appearing from the hollow, both nestlings.