Born in La Porta, Corsica, Sébastiani was the son of a tailor[REF] and well-to-do craftsman,[REF] the nephew of Louis Sébastiani de La Porta, a Roman Catholic priest who was later Bishop of Ajaccio,[REF][REF] and probably a distant relative of the Bonapartes [REF].
Sébastiani joined Lucien Bonaparte's entourage,[REF] and endorsed Napoleon's political actions, taking an active part in the 18 Brumaire coup (9 November 1799) [REF].