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:
Augusta of Saxe-Weimar-Eisenach
Augusta was the second daughter of Charles Frederick, Grand Duke of Saxe-Weimar-Eisenach and Maria Pavlovna of Russia, a daughter of Paul I of Russia and Sophie Dorothea of Württemberg.