Board Thread:Speculation House/@comment-68.186.83.101-20130601225528/@comment-26872876-20160120171742

Yo Gohan, if you want another way to look at it, Qrow is essentially Ruby's Uncle-In-Law (though it's technically not much of a thing) as Taiyang is Qrow's Brother-In-Law.

To start, let's assume Raven and Taiyang had married.

Ruby and Qrow have no direct blood relation, however, she has Yang who's blood related and her father is 'legally' related (in addition to being teammates and friends). Ruby has been given a lot from Qrow. He was allegedly a teacher at Signal and taught Ruby how to use her weapon. This and her reaction to seeing him suggests (basically proves) they get along and care for one another. Thus, she uses Uncle. Even if it comes from the fact her half sister is the only one blood related.

While you Mau not be as close to your Brother-In-Law, Ruby is the opposite. She admires Qrow.