Monaco succession crisis of 1918 of this event, pursuant to the clauses of the treaty of 17 July 1918." The French government at the time was still the Vichy regime. Louis II died on 9 May 1949. The Principality of Monaco passed to his grandson, Rainier III. In the absence of an heir male, the ducal titles of Valentinois and Estouteville became extinct in French nobiliary law. Before Rainier III married Grace Kelly in April 1956, he notified the French government of his plans; the French ministry of foreign affairs replied with a message of official congratulations. Count Louis de Causans is suing the French
Honoré III, Prince of Monaco of Maria Clementina Sobieski. The marriage never materialised and as such, in 1751, he married Maria Caterina Brignole (d. 1813). The couple had two children; Honoré IV, Prince of Monaco and Joseph Grimaldi (10 September 1763 – 28 June 1816) before divorcing in 1770, and Marie-Catherine married the Prince de Condé in 1798. Honoré III, Prince of Monaco Prince Honoré III, Prince of Monaco (10 November 1720 – 21 March 1795) ruled as Prince of Monaco and was Duke of Valentinois from 1731 to 1793. Honoré was the son of Louise Hippolyte, Princess of Monaco and her husband Prince Jacques.