Santos is the father of Justin Suarez and the love interest of Hilda Suarez. Hilda's father Ignacio and Justin both dislike him due to his gambling habit, which gets him in trouble with loan sharks. Ignacio also worries about Santos returning to Hilda and getting her pregnant again, only to leave her again.
In "After Hours," Santos gives Hilda part of his gambling winnings to help get Ignacio a lawyer. In return for the money, Hilda agrees to let Santos visit Justin. Santos misses his first visit with Justin when he is attacked by loan sharks, but safely arrives for the Thanksgiving dinner in "Four Thanksgivings and a Funeral." Afterward, he and Hilda make love, and he sticks around the following day. However, Hilda becomes angry when Santos suggests that Justin play football outside with him; in retort Santos insults Justin's upbringing, and eventually walks out on Hilda.
Santos returns in "Brothers," when Justin calls him from school after being sent home for fighting. Santos finds out it was because Justin was defending his mother after another boy called her a slut. When the boy's mother comes by to criticize Hilda, Santos sides with his ex and his son, saying that Justin was right in protecting his mother. Santos' return leads to hints that he still has feelings for Hilda despite questions of Justin's behavior.
In "Derailed," Santos accompanies Hilda and Justin to a musical. After it looks like they won't make it to the musical because of the blizzard, Justin re-enacts the musical for his dad in a broken-down subway car. When a fellow passenger tells him that he's seen enough (and utters a derogatory comment about Justin under his breath), Santos confronts the man and tells him that his son is going to finish, and he better clap after he's done—showing that Santos is starting to accept that his son is different.
He proposes to Hilda in "Petra-Gate," but is shot by a man holding up a convenience store in the Season One finale. The series ends on a somber note with Hilda learning of her fiancé's shooting.
As of the Season 2 premiere, Santos is shown to be alive and well, recovering from being shot three weeks earlier, however by the end of the premiere this is revealed to be a fantasy induced by Hilda's grief. At the end of the episode Hilda finally admits Santos has died and begins to mourn his loss rather than live in denial.