Over the years I have had trouble keeping the males healthy for very long in some of my most successful set-ups. I refrain from buying them when they become available which is much less than the females for sure. Genicanthus sp. are one of those species that are able to change sex to meet the breeding need. I haven't ever done it myself, but have talked to people that have bought a few females and had one change into a male. In the wild, males and females of some of the species do not pair up and swim together like some of the other angels. Fact is, some female genicantus were thought to be another type all together before someone observed the change in an aquarium.
hth