User blog comment:PUNCHURPREGNANT/Gray and Silver Predictions/@comment-1776824-20140112194221/@comment-7418318-20140112212838

Oops... you didn't mention the father theory, so the whole infertile/incompatible thing really was a mistake. My bad.

But I don't see how Silver being a Demon and having Demon- and Human-shape now makes it impossible for have been Human once, and thus maybe being Gray's brother.

He might have only been transformed into a Demon, rather than being born or created as one.

Cobra may simply have been mistaken. He could have only known about some or maybe even the other 8 of the 9DG being Zeref Demons and just assumed that Silver is also like that.

Or he could have "enhanced" the truth a bit, because with Doranbolt being more scared of the 9DG, he'd be more likely to agree to releasing the OS members.