An illegitimate son of the French statesman Talleyrand and his married lover Adelaide Filleul, Countess of Flahaut, Count Auguste Charles Joseph de Flahaut de La Billardie was a lover of Hortense de Beauharnais and father of the Duc de Morny. His crossdressing granddaughter Mathilde de Morny, Marquise de Belbeuf (1862-1944), created a scandal at the turn of the 19th century by her affair with the French novelist Colette.

He married Margaret Elphinstone, daughter of Admiral George Keith Elphinstone, Lord Keith, and had five children.