Marcus Valencio was an orphan and brought to the human compound in Long Island when he was but a child.
Marcus is the best friend and former boyfriend of Kira Walker. Marcus has a great sense of humor and he utilizes this talent like a 'time-out' during times of great stress.
Prior to the events in Partials, he trained as a medic in East Meadow. Through the events of the series he becomes more involved with Human and Partial relations, acting as a bridge between the two species.
Marcus is of Mexican decent, however his exact ethnicity is unknown due to him being orphaned during the Break.