Board Thread:Improvements and Issues/@comment-5355747-20130313062554/@comment-26420452-20130710085306

It's very unlikely that Ichigo is Kūkaku's/Ganju's/Kaien's first cousin. Matsumoto commented that Isshin was the head of a branch of the Shiba clan, while it's heavily implied (if not stated, I don't really remember) that Kūkaku is the head of the entire clan.