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:
Princess Sophie of Saxe-Hildburghausen
On 6 March 1776, she married at the age of 16 (in Hildburghausen) the Hereditary Prince (and later Duke) Francis Frederick Anthony of Saxe-Coburg-Saalfeld. At the time, Francis was already in love with his future wife Countess Augusta Reuss of Ebersdorf, but he was unable to break off his engagement with Sophie.