Board Thread:News and Announcements/@comment-28288412-20161006192647/@comment-3257939-20161010145123

It's true that his existence wouldn't be relevant until now. Weiss had yet to properly enter the plot. There was really no reason for her to hunt down the Roman Torchwick and the White Fang. Sure, she hates the group but never considered the idea of taking them down herself until Blake tried to do so on her own and, as a teammate, Weiss couldn't leave her alone. She and the rest of the team got in because of Blake.

And now that Blake's story is no longer the main plot and Weiss finally has her own, it makes sense that they reveal the full background. We still don't know anything about her mom, and Winter's existence was unbelievable a few volumes before, what's the problem with a little brother?