 Through his father, Domenico was related to Marchese Camillo Serafini, who served as the first and only Governor of the Vatican State (1929–1952).Serafini entered the Order of Saint Benedict in 1871, joining the Cassinese congregation.He made his profession on 16 June 1874 and studied at different Benedictine houses of studies and the Pontifical Gregorian University, where he obtained his doctorates in philosophy and theology.