User blog comment:ChishioKunrin/Grimm-mask Samurai Woman = Yang's Mother/@comment-144.137.204.188-20141024203650/@comment-24994749-20141025010245

Well, for once, he was part of the same team as papa Taiyang and mama Summer who did stick around.

Second, Summer threated Yang as her own daughter to the point Yang only learned she wasn't after Summer's death.

Third, he was a teacher of both Yang and Ruby at Signal and tutored Ruby in the use of his signature weapon personally.

Even if they are not blood related and Ruby is aware they are not blood related, the bond is close enough he might be thought of as an "uncle" in an honorary sense.