François-Léon Clergue was born in Lavaur on 23 December 1825 as the first of three children to Jean-Louis-François-Frédéric Clergue (1798-1872) and Rose Amilhau (1797-1867); his baptism was celebrated moments after his birth in the names "François-Auguste-Léon. His father - a devout law clerk - consecrated him to the Blessed Mother following his birth. His mother later earned the nickname "La Vendéenne" in 1830 after the riots when she grabbed the revolution's flag from some adolescents parading it around the streets. His brother was Ciprien-Célestin and his sister was Marie Jeanne Mélanie (1833-1872) who both predeceased him. His brother died in Istanbul while in the armed service following the amputation of his right leg.