Not much is known about Marius's true background. Marius grew up with a mother who was addicted to drugs and no father. He has taken care of himself and his little brother Eddie since a very young age.
In a scene in Pilot, Marius remembers cooking mac'n cheese for his brother in a poor apartment while his mother sits in the background, appearing hungover.
Marius has spent approximately three years in prison, sharing a cell with Pete Murphy. Two days before his release, his brother Eddie warns him not to return to the city and advises him to hide out somewhere as they owe gangster Vince $100,000. Marius decides to adopt the identity of his cellmate Pete, who is not up for parole for another two years. In their past three years as cell mates, Pete has told him countless stories of his grandparents' farm and their blooming bond business. Since Pete has not seen his grandparents for over 20 years, Marius succeeds in making them believe he is their long lost grandson when he turns up at the farm. However, it turns out the family is not in the financial bond business, but rather runs a small bail bond business, which does not hold the kind of money Marius had hoped for. (Pilot)
- Whilst pretending to be Pete, Marius claims to the Bernhardt's that he has spent the past years doing investigative work for an insurance company, like tracking down valuables and skiptracing.
- "I'm a confidence man. I give people confidence, they give me their money. ("Pilot")