Sebastian was the result of a rocky whirlwind of a relationship between Wilson Go and Christine Park. He was a drug dealer and she just so happened to buy from him with means other than money. They had never intended to stay together, but her pregnancy and Sebastian's birth forced them to settle, if only temporarily. Neither of them were fit to raise kids. Wilson was an angry man prone to violent outbursts and Christine was too preoccupied with her addictions and various other problems to care, but several years later she gave birth to a daughter, and shortly afterward Wilson went to jail.

By then Sebastian had long learned to stay out of the apartment. He spent most of his time with a group of older kids who lived in the area, and they taught him how to steal and perform other petty crimes. At first it was to fit in and have fun, but he quickly realized how lucrative it could be. There weren't many other options for a young boy to earn money even if he resorted to them too. After all, they were in desperate need of it. His mother alternated between working and periods of depression with increasing frequency, until one day he came home to find her dead in her bedroom.

He simply shut the door and started handing his baby sister off to an elderly woman who lived down the hall, but this routine didn't work for long. Not even two days later he was caught trying to steal from a car, and after finding out about their unfortunate home situation Sebastian and his sister were placed into the foster care system and separated to different families. Despite being an eager, well-meaning but mischievous child, Sebastian was often accused of being a rebellious troublemaker. Old habits died hard and eventually he gave up defending himself, and as a result he frequently shuffled between families.

When he turned eighteen Sebastian spent a few years trying to leave the city, where he managed to scrape by through odd jobs and shacking up with someone who had a steadier paycheck. Things tended to go awry though and he would sooner or later find himself in Boston again. Eventually he gave up the notion of leaving, and began working to save up money to settle down instead. Once his sister graduated high school and the foster care system he moved them to an apartment—a cramped, rundown space that had an awfully outdated air conditioner, but it was theirs. They've been living together ever since.

These days he works as a barista at Starbucks, purposefully misspelling names of rude customers or annoying friends. On weekends and sometimes after his shift at the cafe he apprentices under a piercer at a parlor in hopes of eventually making it his full time gig. He's pretty rough around the edges and his humor is often at someone else's expense, but he enjoys interacting with people even if he isn't quite so friendly. What's the fun in being nice all the time? Most people don't even deserve it anyway.