User blog comment:TheBody84/Ichigos father being the former Kenpachi/@comment-1659217-20091024222204

I think Isshin took up the name Kurosaki upon marrying Masaki. Thus no-one in Soul Society knows the Kurosaki name and Urahara does call him Isshin - Not Kurosaki. I also think that Isshin is former royal guard as they are all captain level. As any captain met Kurosaki Isshin ? ever?