 They soon became lovers.In 1811, at an unspecified inn in Switzerland, close to Lake Geneva, Hortense secretly gave birth to a son by de Flahaut,
Charles Auguste Louis Joseph ( 21 October 1811 - 10 March 1865), created Duke of Morny by his half-brother, Napoléon III, in 1862.Only her brother Eugène, her closest companions, and Adélaïde Filleul de Souza (Charles de Flahaut's mother) were aware of her pregnancy and the subsequent birth.