Board Thread:Questions and Answers/@comment-6207546-20130504124857/@comment-25130979-20140702122233

Isshin must not have been a captain for very long then because, if you search the Shiba Family lost nobility after its most notable member (Kaien) died, had Isshin already been a captain, there is no way the Shiba clan could have collapsed, or at least, not for that reason.

Also its pretty hard to believe that Rukia never heard of Isshin, considering all that she put the Shiba Family through i think that she should at least notice when a Shiba is captain. Also, arent nobles supposed to be well educated pertaining to who stands at the top of soul society, i mean all the other nobles seem to be well informed about the people who stand at the top.