Board Thread:Questions and Answers/@comment-25801533-20150531094407/@comment-11051098-20150601204455

I dunno with the manga, but in the anime, Ganju was just a little kid when Rukia brought Kaien's dead body back to his family.

I think it's safe to assume that Kaien died at least, I don't know, 40-50 years before the story began.