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:
Duke George of Oldenburg
On 3 August 1809, George married Grand Duchess Catherine Pavlovna of Russia, the fourth daughter of Paul I of Russia and Sophie Dorothea of Württemberg and favorite sister of the Emperor Alexander I of Russia. The events behind their marriage began when Napoleon Bonaparte, hoping to secure a Russian alliance as well as a male heir, hinted his desire to marry Catherine after finalizing his divorce with Empress Joséphine. This so horrified the Russian imperial family that Catherine's mother immediately arranged her marriage to her cousin, Duke George. The day the marriage occurred, Duke George received the style "Imperial Highness" and was appointed the governor-general of the three central provinces of Tver, Yaroslavl and Novgorod.