Board Thread:Speculation House/@comment-137.112.144.92-20141024021604/@comment-118.92.145.248-20141027022535

Quite simply;

Mysterious Swordswoman = Yang's mother (why else would she care enough to save her)

Mysterious Swordswoman = Adam's mother (hence the resemblence in appearance and weapon)

Ergo Yang and Adam are half-siblings, Adam has no relation to Ruby since different dad (his dad being a Faunus).