Many people put in too much information when writing a biography - or at least, too much of the wrong kind of information !!
When an Artist is signed to a Record or Publishing deal, on one level or another it will be because of their personality as well as their music. So, a biography needs to be a reflection of the person and their music.
There are no right or wrong ways of constructing a biography, but it should ideally be one page accompanied by a couple of photographs (which will also reflect the Artists personality).
It is OK to mention your background and upbringing, but only in passing: nobody cares where you went to school and nobody cares how out of place you felt in your suburban commuter town (it's a cliche for artists !).
People definitely care about what makes you tick. Why you create the music you do. Avoid the hard sell though - "we're going to be huge in a years time". It sounds so amateur.