The massive
announcement for the revamp did confirm that they can breed:
For three, remember those Ancient Kuhnas you bought? Remember how they gave you those amazing bred Ancient Kuhnas... but how those bred Ancient Kuhnas couldn't breed to anything? That's all in the past. If your Heiv Kuhna or your Nuvuldan Kuhna ever had a lifemate, they can now breed like any other Generation Kuhna! They carry Ancient genes like their parents, together with the recessive of their respective line (so Nuvuldan would be Ancient x Spectra when you breed it). No more potions! No more sadness!
The only Kuhnas that still cannot breed normally are customs, which do still require a Fortuity or EoF in order to breed, or to be bred with an Elder.