Sam is Henry's 13-year-old brother, a quiet, anxious kid who becomes Ellie's first friend her own age on the road. You travel with him from the hideout in Pittsburgh through the sewers and suburbs in The Suburbs.
Sam tries to act grown up, taking inventory of the group's food, but he is still a kid who wants the toy robot he finds in a Pittsburgh toy store. He is more pessimistic than his brother, doubting the rest of their group survived and doubting Henry's talk of heaven. He is openly scared of the infected and wonders whether people are still trapped inside them.
Sam works much like Ellie as a companion. He can throw a brick to knock a stalker off Joel, Joel boosts him to fetch ladders, and in the sewers he crawls through an opening to clear a pipe blocking the door, then goes through a window with Ellie to open a locked one. In the nursery area of the sewer camp he talks about how he used to draw.
In the suburbs a clicker scratches Sam's leg before Joel can kill it, and he tells no one. That night he admits to Ellie that he is afraid of becoming one of the infected; she gives him the toy robot, which he tosses aside once she leaves. By morning he has turned. He attacks Ellie, Henry shoots him, and then takes his own life. Ellie keeps the robot she meant to leave on his grave.
Henry
Henry is a young survivor from Hartford who is trying to get his little brother Sam out of hunter-held Pittsburgh. He and Joel get off to a bad start in a brawl, then team up to escape the city, and he fights beside you through the end of Pittsburgh and The Suburbs.
Ish
Ish is a survivor you never meet in person: you learn his story from a trail of notes in The Suburbs, from his wrecked fishing boat on the riverbank to the sewer camp he built under Pittsburgh. Picking up his notes in order tells how one lonely man built, and lost, a community.
Kyle
Kyle is a father from the Pittsburgh suburbs who joined Ish's community in the sewers. In The Suburbs you learn his story from the Looting note and the Cornered note, and Ish mentions him in the Rain catcher note.
Susan
Susan is Kyle's wife and one of the founding families of Ish's sewer community under Pittsburgh. In The Suburbs she appears only in notes: the Rain catcher note written to her and the Survivors note written about her.