Board Thread:Episode Discussion/@comment-24666470-20160110195733/@comment-4010415-20160110204034

It was pretty obvious that they're siblings. Ruby and Yang refer to Qrow as their uncle, and Raven is Yang's mother, soooo what does that make Qrow to Raven? Her cousin? Ha, no. They couldn't be anything other than siblings.

It's also likely that they're twins.