Board Thread:Dark Souls II/@comment-90.220.93.142-20140316211638/@comment-24684538-20140316224953

It's never stated it is Ornstein but the Leo ring and the fact he looks like Ornstein makes it very likely that it is Ornstein. It could be that Ornstein was an Illusion in Dark Souls 1, afterall only Gwyndolin and the Darkmoon are still in Anor Londo.

Also, if you kill Gwynevere (or whatever it's spelt like) you'll find 2 knights outside the Ornstein & Smough boss room, a Berenike Knight and a Balder Knight. It could be that Gwyndolin allowed these two to take the ilusory form of Ornstein (Balder Knight) and Smough (Berenike Knight).