Board Thread:Speculation House/@comment-14138255-20141031002615/@comment-24198837-20141210210204

Well, going with that DnD comparison I always like to make, it's entirely possible that Taiyang is a "Druid" character and Zwei is his animal companion. Assuming that Taiyang is "20th-level" or higher, Zwei should be the same.

However, considering that Ruby, even though she has the heart of Palidin, fights like a Ranger, it's most likely that the person who trained her was one - and fun fact, Rangers can choose to bond with an animal companion.

So Zwei being Qrow's doesn't seem like a far fetched idea, and if he is an animal companion, it would explain his power, because he'd be Qrow's level. (Well, it would actually be Qrow's level minus three because he's not a druid, but that would still put Zwei on at least level 17, and going on an assumption Maki made, RWBY would be level 5-7 max).