all I know is some rudimentary info about Yoshio, but nothing one couldnt find out searching the web for a few minutes ^_^"
before his time with Ayu, Yoshio Nomura was apparently part of a "boy-group" called The Good-Bye and also had also his solo work produced.
there are some reissues of his works at
CDJapan
Official Site (or official SIGHT as it is written there
)
^if you know Japanese maybe you can get some info there, otherwise I cant help you
as this is all I know as well ^^