William I of Württemberg
On 24 January 1816, in Saint Petersburg, he married his first cousin, Grand Duchess Catherine Pavlovna of Russia (1788–1819), daughter of Emperor Paul I of Russia (1754–1801) and Princess Sophie Dorothea of Württemberg (1759–1828). The couple had two children:
Duchess Sophie Adelheid in Bavaria
Her parents were Karl Theodor, Duke in Bavaria, head of a cadet branch of the Bavarian royal family, and an ophthalmologist of recognized reputation, and his second wife, the Infanta Maria José of Braganza, third daughter of King Miguel I, exiled monarch of Portugal. Her paternal aunt was Empress Elisabeth of Austria ("Sissi"). She was also the sister of Queen Elisabeth of the Belgians, consort of Albert I and of Marie Gabrielle, wife of the last crown prince of Bavaria, Rupprecht, later the head of the House of Wittelsbach. She was named after her father's first wife, Princess Sophie of Saxony, the mother of her half-sister Amalie.