Marie Bonaparte was a great-grandniece of Emperor Napoleon I of France. She was the only child of Roland Napoléon Bonaparte (1858–1924) and Marie-Félix Blanc (1859–1882). Her paternal grandfather was Prince Pierre Napoleon Bonaparte, son of Lucien Bonaparte, 1st Prince of Canino and Musignano, Napoleon's rebellious younger brother. For this reason, despite her title Marie was not a member of the dynastic branch of the Bonapartes who claimed the French imperial throne from exile. Her maternal grandfather was François Blanc, the principal real-estate developer of Monte Carlo. It was from this side of her family that Marie inherited her great fortune.