Well… pretty much there was a theory on reddit that posited the Reynes as a bastard branch of the Casterlys, an idea whose link was included in the wonderful post of @joannalannister in her words for House Reyne. That was pretty much why I said it.

Also, when I spoke, I meant how Ellyn Reyne does resemble Barbrey Ryswell. Ellyn Reyne wanted to become a Lannister with much more intensity than anyone else recorded, like Barbrey and Theon wanted to be Starks above all.

Ah, I see. It’s a fine theory as it goes, the whole reversed arms thing, but the WOIAF I think is pretty strong evidence to the contrary. I’d also point out that we don’t know what the heraldry of the Casterlys was, and that if the connection was through the Casterlys, why would they have reversed the sigil of the Lannisters? 

I don’t know if I would agree that Ellyn wanted to become a Lannister, exactly. She “had for years anticipated one day being the Lady of Casterly Rock,” and certainly pursued Tywald and Tion and even Tytos.

But Ellyn doesn’t show any of the signs of alienation from her original family that, say, Theon did. As “the Lady of Casterly Rock in all but name,” Ellyn made damn sure that House Reyne profited from her success with Tion. Hence “her brothers Roger and Reynard were ever at her side, and offices, honors, and lands were showered upon them, and upon her uncles, cousins, and nephews and nieces as well.” Likewise, when she was finally exiled from Casterly Rock, Ellyn promoted the fortunes of Houses Tarbeck and Reyne as much as she could, shaking down Tytos for as much gold as she could get, putting it in to Tarbeck Hall and its surrounding lands. 

So I think of Ellyn as more self-possessed than Theon and less bitter than Barbrey. Which I think means that she didn’t necessarily want to be a Lannister, but rather wanted to be the Lady of Casterly Rock and the mother of the next Lord…regardless of whether this was as a Lannister or as a Reyne or as a Tarbeck.