@Apple: Well, for the sake of the fic the story is... well, the fic is largely inspired by
Bat Boy The Musical. It's also partly inspired by the Who's Eminince Front, but that's beside the point.
Basically, the guards we saw are the only two known of, and are for all intents and purposes a new species. They were found feral in Canterlot, where a scientist took them in to study them, discovered they were intelligent, and started educating them, a la Tarzan. They melded in with high scoiety for a while before being chased off, whereupon Luna took them in as her personal guards, chauffers, advisors and general go-to ponies.
The reason they were chased off by the gentry, by the by, is that they're omnivorous predators, alongside just generally having bad habits of being unsuspectingly spooky.
Your fanon is actually really cool, though, for the whole thing.