User blog comment:PUNCHURPREGNANT/Gray and Silver Predictions/@comment-1776824-20140112194221/@comment-7418318-20140112210745

Whoops, right... you didn't mention the father theory, my bad.

But still I don't see how him being a Demon now and having both a Human and Demon form (again now) would make it absolutely impossbile to be Gray's brother, since he might have been turned into a Demon at some point, rather than being born/created as one.

The same probably counts for the future theories too, but with Gray's scar missing from Silver's face, we can pretty much discard that theory.