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 Sophia Dorothea of Prussia
Princess Sophia Dorothea of Prussia () (25 January 1719 – 13 November 1765) was the ninth child and fifth daughter of Frederick William I of Prussia and Sophia Dorothea of Hanover. By marriage, she was a Margravine of Brandenburg-Schwedt.