Quote Originally Posted by Cilia View Post
(People will still imagine Hyur (Humans) can interbreed with just about anything, as is their wont.)
The game occasionally uses the word "humans" to refer to all of the player races collectively (and presumably Garleans, as well), which leads me to believe that the racial variants are similar to breeds of dogs - sometimes dramatically different in appearance, but all the same species and all technically interfertile. (I say technically because, while genetically compatible, sheer physical differences may make some pairings incompatible.)

However, admittedly it IS the case that all known half-breeds (Hilda, Arenvald, and the unnamed legendary Au Ra princess) have been the result of Hyur-plus-other, so you could be right.