That heir was his cousin, Wilhelm, 2nd Duke of Urach, who, although born and raised in Monte Carlo as the son of Princess Florestine of Monaco, was a German subject, property owner and patrilineal relative of the kings of Württemberg.

Louis adopted Charlotte in Paris on 16 May 1919, thereby entitling her to the surname Grimaldi, while her grandfather bestowed upon her the traditional title of the Principality's heir, Duchess of Valentinois, for life.

[4][5] Charlotte became heir presumptive to the throne as Hereditary Princess when her grandfather died and her father inherited the princely crown in 1922.

The couple had two children: Their marriage was not, however, a happy one; they separated on 20 March 1930 due to his homosexuality, and Charlotte left him to live with her doctor and Italian lover, Dalmazzo.

After her son assumed the throne (in 1949), Princess Charlotte moved to live at Château de Marchais, the Grimaldi estate outside Paris.