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:
Countess Palatine Dorothea of Simmern
She married on 21 February 1595 in Heidelberg to Prince John George I of Anhalt-Dessau (1567–1618). She was his second wife. She was led to the altar by her guardian, Elector Palatine Frederick IV. Under her influence, her husband openly converted to Calvinism in 1596. After his death, she retired to her widow seat Sandersleben Castle.