Okay i was rewatching bleach and got to Kaien Shiba part. Maybe I'm the first but what if Isshin Kurosaki name is really Isshin Shiba. Remember how Kukaku Shiba treats her brother Ganju and then look at how Isshin treats Ichigo. Maybe the Shiba clan beat up the men to make them stronger. Then look at Kaien Shiba and Ichigo and that they are drawn the same way. Remember that the author had Shinhi Hirako on the cover of Vol.1. Kaien and Ichigo are so much alike the they could be part of the same clan. And the last reason a think is that if Isshin was a captain than Byakuya Kuchiki would of heard of the kurosaki name. I think that it was Isshin that took his wife's name and that was the reason that Byakuya didn't know the Kurosaki name. By the way during the manga and anime well are informed the the shiba clan fell from power or something along those line. Maybe that had something to do with Isshin and the reason way he went to the living world or the fact that he married Misaki caused the problem.