Kaya and Kioni were both born around the same time (in the late 2000's), and it's likely they at least therefore shared the same father and then potentially the same mother (Kijani), as they both share 'K' names.Obi is the son of Bwana, but is likely related to Kaya via his mother Kioni. If Kaya’s mother is indeed Kioni that makes sense as the K initial may indicate a shared lineage. This tradition was used at Auckland and Hamilton for many years. Makes a change from giving them Z names because they’re zebras.
It’s a real shame to see how the efforts of Auckland (Grant’s) and Werribee (Chapman’s) have gone to waste in the last decade or so due to the region being content to hybridise. I think priority should be either establishing small breeding herds as you suggest; or replacing all generic breeding stallions of large herds with purebreds. These stallions are typically in place for a decade or more and purebred mares (the scarcer commodity) can be added as and when they become available.
At the present, the focus should be on maintaining the current purebred herds. It's good to see DDZ holding multiple groups to allow a continuation of breeding rather than sending stock off to other regional facilities where they will be hyrbidised.
More imports would obviously be needed; but I see no reason why a zoo like Werribee can't go and acquire some additional stock to form their own herd. Their current breeding stallion is the older half brother of their former stallion making him very closely related to all of the younger fillies.