i don't think he has any concrete reason to dislike his name, he just has weird interpretations of what it means to be 'cool', kids probably mispronounced his name in middle school and he just became fixated on changing it. his father just wants him to be happy so he went along with it.

fabio is his older brother, by 8 years. they have a pretty strained relationship as fabio is kind of weird and 'in his own world' most of the time. he introduced flynn to mr. bungle. fabio supports flynn's musical endeavors but he's also trying to push him into joining his cult's choir.

fabio has hemokinesis. engages in bloodletting for artistic and spiritual reasons. contrast this to flynn's extreme case of hemophilia