He was the son of Jean Lannes, 1st duc de Montebello, Marshal of the Empire, who died from wounds received during the Battle of Essling on 22 May 1809, and his second wife, Antoinette Scholastica Guéhenneuc. He was made a peer of France on 27 January 1827 by Charles X in consideration of services rendered by his father, however he took his seat at the Palais du Luxembourg (meeting place of the Chamber of Peers) after the Revolution of 1830. In the meantime, he had traveled to the United States, then was attached to the Embassy of France in Rome, with the vicomte de Chateaubriand.