So I say that qrow is her biological father whereas taiyang is just the fatherly figure. The story that goes along with that would be after a night of fun (wink wink nudge nudge ) with summer he goes on his mission to protect the maidens. Summer not wanting to get in the way of qrow's mission dose not try to inform him . Eventually she starts to panic about having a kid. Taiyang having had a kid of his own helps her through it securing the role as the fatherly figure. Qrow comes back to a young Ruby causes some questions. So having lost the role as father he becomes her uncle instead. Myth busted!