Although he was not an heir to the French throne, general Claude François de Malet attempted a coup in France, in 1812. After escaping from captivity, he informed the National Guard that Napoleon had died in Russia. He succedeed to release two generals, arrested a few others and tried to seize the power in Paris. The same day, he presented letters to Colonel Pierre Doucet that stated Napoleon had died on 7 October. However Doucet had knowledge of letters written by Napoleon after that date and went suspicious.
Shortly after, Malet was arrested and then executed.
Article from wikipedia : Malet coup of 1812