Board Thread:Questions and Answers/@comment-6608477-20130220070043

I always wondered about his past but nothing really panned out till now.

Reading up on the latest Arc I've come up with this and it kind of fits.

Knowing now that Retsu Unohana being the Capt. of squad 11 for a time leaving squad 4 open. So during the time Unohana was in 11th, Isshin was Capt. of 4th. That is why in the Human world he is a doctor.

Also I think Masaki his wife being a Quincy, was Ryuken Ishida sister making Uryu and Ichigo cousins, which will really make Uryu mad! lol

Anyway those are my thoughts on Isshin's past.  