Board Thread:Improvements and Issues/@comment-5355747-20130313062554/@comment-11477779-20130720221348

Isshin and his children are all related to Kukaku and Ganju (and Kaien). What the direct relationship is we don't know for sure yet. The similarities between Kaien and Ichigo were established LONG ago and noticed by several people. I can't say if Kubo really planned things out like that from the beginning or just found a fortuitous way of tying the strings together. Seems to have worked out pretty well though! What's a bit odd is just how low a profile Isshin kept in those 20 years after. Maybe Urahara had a hand in keeping him hidden from the Soul Society. Pretty much EVERYONE in the Gotei 13 should recognize him. There are only as many as 13 captains at any given time. They should be known by sight and reputation by all active shinigami. Rukia is 150 years old, and was certainly in the 13 court guard squads when Isshin was still a captain. Why didn't she recognize him? You could argue that the different squads didn't fraternize much but everyone should be familiar with the captain and lieutenant of each squad.