Well, mostly I, too, do not want my theories to be true! But, anyways: had they used only 2 spanish actors in a cast of latin americans it was possible the characters were related. This way they chose the most “mexican-looking” to play mexicans and the blue-eyed girl to play young Grace who could still be passing as american. And maybe the hair-dyeing is a thing that happened because of the enhancement? Idk. Analyzing the cast to prove plot points is always dicey, so I’m guessing we gotta wait.