Board Thread:Questions and Answers/@comment-27449779-20151222131224/@comment-26269901-20151222142901

Kaien was killed before Isshin met Masaki. The clan lost their status as one of top nobles after Kaien's death, though I don't know if it was because of it, or it was just part of the reason. We don't know how close Isshin was to Kaien and his siblings, with him being from branch family they didn't necessarily live together, so any guess is just as good.