I was watching a YouTube video by some guy named Michael where he pointed out all the times that the Others were compared to shadows and postulated that they're ice-based shadow babies, as like counterparts Melisandre's fire-based shadow babies. Do you think that could be what George is going for?
It's an interesting theory, but GRRM has already explained what's going on with the Others:
I had many talks with George. [...] He spoke a lot about what they were not, but what they were was harder to put into words. Here is what George said, in one e-mail: "The Others are not dead. They are strange, beautiful… think, oh… the Sidhe made of ice, something like that… a different sort of life… inhuman, elegant, dangerous." —Anne Groell
The shadow babies appear to be a magical conjuring made from a piece of the father's lifeforce, that is gestated in Melisandre's womb, and that dissipate after they have accomplished their task. They are not really alive, as such, not really real. But the Others are alive, they're living beings. Strange, not human yet humanoid living beings, people like ice elves from somewhere else (the heart of winter, beyond the curtain of light at the end of the world). And they can be killed, by fire-imbued weapons of dragonglass or dragonsteel. To make it more clear, the Others use magic, they are magical beings in the way the Children of the Forest or dragons are, but they are not entirely made of magic like the shadow babies are. Do you see the difference?
But do the Others have similarities with shadow babies? Sure. They're both killers, although the Others have their own intelligence rather than being animated by another's will. (For that, compare the wights, of which the human ones probably do not retain much of the consciousness of the original living person.) And they both move magically, literally as a shadow for the shadow babies, and like shadows for the Others. (Perhaps there's a bit of teleportation involved? That could explain things.)
Nevertheless, the true fire-based counterparts to the ice-based Others, like fire wights parallel the ice wights, fire made flesh as the Others are ice made flesh, is the dragons. That's what the core of the conflict, the song of ice and fire, is all about. In the end, Melisandre's shadow babies are merely a tool, a distraction, a minor sub-plot in the grand story of it all.
