The GMG are no longer Kusari nationals, though they originated there and have strong cultural ties to Kusari. The GMG "ethnicity" is also very similar to that of Kusari, but they are not exactly Kusarians.
The above has been true for decades at bare minimum- likely much longer. It took some time, but it happened. The Mollys are similar, though their transition was enforced by violence. Mollys have their own stable population, and are no longer ethnically Bretonian, nor considered Bretonian by anyone in the region.
I think there's two ideas in this thread, and I want to make sure I know which one Marburg had in mind- are the Gaians recruiting from other houses than Bretonia, or has their population been distinct enough from that of mainstream Bretonia that they are no longer Bretonian in ethnicity? Or, perhaps a third take on it, are the Gaians no longer viewed as Bretonian in nationality, but instead as their own independent non-House entity like the Mollys are? None of these options are mutually exclusive, it could be any combination of them.
Also, important question. How big, population-wise, are the Gaians? Can we get an order of magnitude?