Smith family

Living inside Wall Rose, the Smith family produces one of the most consequential figures in the fight for humanity's survival: Survey Corps Commander Erwin Smith. Both of its recorded members die chasing the same forbidden question about the world's true history.

Erwin's father teaches school, with his own son among the pupils. Pressed by a question the boy raises in class, he privately shares a dangerous idea: the official history books hold so many contradictions and gaps that humanity's memories must have been erased at some point, which would explain why no account of the Walls' construction exists. The theory costs him his life, and it plants in Erwin the drive to uncover the world's origins and prove his father guessed correctly.

Erwin enlists in the army and moves on to the Survey Corps, where he devises the Long-Distance Enemy Scouting Formation. Keith Shadis initially rejects the tactic, but it becomes the standard for every expedition after Erwin rises to Commander. During the uprising against the Royal Government, he recounts his father's fate to Commander Pixis. Dying after the battle for Shiganshina, Erwin lashes out in delirium, hysterically repeating the question he once asked as a schoolboy; hearing it, Levi Ackerman chooses to give the lone Titan injection to Armin Arlert instead, believing this finally lets Erwin rest.

Only two members are recorded, and neither survives the story. Erwin Smith commands the Survey Corps until his death at Shiganshina, while his father, a civilian teacher, is killed years earlier over the theory he passed to his son.