Board Thread:Questions and Answers/@comment-11927664-20130730160308/@comment-24146394-20131108220006

I mean it's highly doubtful and won't believe it till I see it, but would explain why they look so similar and why Rukia bonded so quickly with Ichigo.

Believe only the hollow went back to Hueco Mundo. He might of merged enough with Kaien to learn his memories, but before he was seen dying in Rukia's flashback he had his soul back.

Still doubtful though and only theories till TK says yes or finishes his story without mentioning it (no).