User blog comment:Lia Schiffer/435: Panic at the Dollhouse/@comment-44061-20110204043111/@comment-1268838-20110204052321

It only makes sense. Ginjo first said "parents," and specifies "mother" only because she is the one that gives birth. With Isshin being a Shinigami, he could have easily fought enough Hollows to have been "infected" with their residual power. Whether this is the case or not, I think it would be wise to give Kubo the benefit of the doubt. Fullbring got introduced all of three chapters ago - I highly doubt that we have been told the full story. That has been the case for Zanpakuto and Resurreccions in the past.