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.
After the runner and clicker ambush in the Sewers, go into the utility room on the right; the note sits by the rain catchers on the back table. Ish praises Susan's idea, admits he gave the kids water guns and has been soaked all day, and invites her to dinner.
In the last house you explore in the suburbs, check the computer desk in the first upstairs bedroom on the left. Ish writes that one open door let a horde into the camp.
Ish says Susan lost her children in the attack and that he had to hold her back from running in after their bodies. She escaped with him and a few children, and he vows to stay strong for her sake. Where they went next is never revealed.
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.
Sam
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.