Though there is a natural closeness between many biological family members in the book—such as Pulga and his mother, Pequeña and her mother, and Don Felicio and his son Gallo, Sanchez highlights a strong theme of characters who feel a close kinship through friendship and circumstance.

Pulga thinks of Chico and Pequeña as his closest family members (after Consuelo), although they are not related by blood: “Pequeña is […] my cousin, but not by blood. Just like […] Chico is my brother, but not by blood. Blood doesn’t matter to us unless it’s spilling” (7). Pulga has an aunt in the United States who sends him money, and as he journeys northward, he reveals that he listens often to the mixtape with his Mexican-American father’s voice, indicating some familial connection to his destination. By comparison, however, he is much closer to Pequeña and Chico; the close bonds he feels with them are very strong and grow only stronger as the three run away together and are bonded by traumatic experiences. They look out for one another; they wake each other up on the roof of the train, trying to keep one another safe; when Chico dies, Pulga refuses to leave his gravesite until Pequeña forces him to do so, and when Pulga gives up on the journey with the border only a night’s walk away, Pequeña refuses to abandon him until he falls into border patrol custody.