Fages married Eulalia Francesca Josepha Callis on June 3, 1780 in Mexico City. Born October 4, 1758 in Barcelona, Spain, Eulalia was a full generation younger than Pedro Fages. She journeyed to Mexico City with her mother and brother to join her father Agustín Callis, captain of the Free Company of Volunteers of Catalonia formed to suppress rebellions by Pima and Seri Indians of Sonora. In 1781, Eulalia and Pedro traveled to Arizpe, Sonora, where Eulalia gave birth to her first child, Pedrito.