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:
Sophia Palaiologina
The marriage between Sophia and Ivan III was proposed by Pope Paul II in 1469, probably with the hope of strengthening the influence of the Catholic Church in Russia, or the unification of the Orthodox and Catholic as was stipulated in the Council of Florence. Ivan III's motives for pursuing this union were probably connected with the status and rights of the Greek princess over Constantinople. The idea of this marriage perhaps was born in the mind of Cardinal Bessarion.