Doc grew up right between TailLight and the spaceport slums, where his parents eked out a modest living. They were poor, but he never felt like it mattered. When he got old enough to enroll in school, his parents were lucky enough to win an education lottery and could send him to study in Prospect Hills.
There, Doc befriended the children of many prominent gang leaders and influential people in the city. To them Doc was just the friend that sometimes needed help with lunch money; but if you ever needed him, he would come running.
It makes sense that he ended up going into medicine, his neighborhood was surrounded by the people who needed help the most.
When his parents died, he opened up a small clinic in TailLight, helping people and doing his best to keep them all safe from the ills that came from the rich who frequented from Vision Minor.
As a result he was somewhat of a people's champion, and all the gangs knew that if you messed with anybody Doc was taking care of you'd get it from the top down. He took in everyone; if you needed to be patched up at 2AM with no questions asked, you called the Doc.