The key defining traits of the Gerudo are red hair and golden eyes. All of them, with no known exceptions, have these traits. The generic guards and elite warriors in OoT and MM, Nabooru the Sage, Telma in TP… and, of course, Ganondorf in every one of his incarnations. Knowing this, what does Groose look like to you? The same red hair and golden eyes.
Now, when Groose lands on the surface, the Old Woman tells him that he has a role to play in the Goddess’ prophecy. It’s clear his role is to aid Link in his struggle to contain and defeat Demise, but what if his role doesn’t end there? What if Demise’s curse upon the bloodlines of Link and Zelda extended to the others in the immediate vicinity, such as Groose?
Just as Link, Zelda, and Demise would be constantly reincarnated, so too would Groose. When the curse hypothetically took root in Groose, it fed off the angry emotions towards Link that Groose felt in the past. This anger and hatred would subtly pass down to every one of Groose’s ancestors, eventually manifesting completely in Ganondorf, who is born out of the curse.
Despite their eventual friendship, Groose unwittingly became the catalyst of Demise’s curse and doomed the future of Hyrule. Indeed, the Four that saved the world ages ago (Link, Zelda, Impa, and Groose) were all bound by the Demon King’s curse, doomed to be forever reincarnated, doomed to all fight the same battle again and again…
There is also a theory that Zelda, as Hylia, would have detected that Groose’s offspring were now damned to produce evil, and in order to slow the rise of this bloodline, cursed Groose to only produce female offspring. But Hylia’s power wouldn’t have negated Demise’s entirely, ensuring, eventually, evil would spring from the loins of Groose. To save face, Groose forced himself into exile in what would eventually become Lanayru Desert, which is how the Gerudo race evolved into what it became.
But there may be evidence to suggest that the Gerudo existed before the events of SS. However, with the Gerudo being nearly exclusively female, they must find males from other races to procreate with. Groose could have been one of such males, passing down the curse through the generations before it manifested in Ganondorf.
What do you think about this?