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:
Dorothea Marie of Saxe-Gotha-Altenburg
Dorothea Marie of Saxe-Gotha-Altenburg (22 January 1674 – 18 April 1713) was the wife of Ernst Ludwig I, Duke of Saxe-Meiningen. She was the daughter of Frederick I, Duke of Saxe-Gotha-Altenburg and his first wife, Magdalena Sybille of Saxe-Weissenfels. She married Ernst Ludwig I on the 19 September 1704.