Ildefonso Schuster (born Alfredo Ludovico Schuster) was born on January 18, 1880 in Rome, Italy, the son of Giovanni (Johann) Schuster, a Bavarian tailor and double widower, and Maria Ana Tutzer. Schuster's sister, Giulia, entered the Order of the Daughters of Charity of Saint Vincent de Paul. Schuster also had three half-siblings from his father's second marriage. As a young child Schuster was briefly kidnapped. He served as an altar boy at the church of the Teutonic Cemetery, next to St. Peter's Basilica.