I saw this on EQD and people are already going absolutely coo-coo bananas over it.
I think it's pretty neat if it's true. It's always cool to see the characters' families, plus it could mean that we get more G1 Twilight in the mix!
I just say that from a storytelling perspective, it'd be nice to get a few hints that he at least exists before he shows up. So that it's not dropped on the audience like "O HAI Twilight I'm your long lost brother that was never mentioned up until now but now I'm here so just pretend I always was welp off to marry a princess KTHXBAI".