Peter III of Russia
Empress Elizabeth arranged for Peter to marry his second cousin, Sophia Augusta Frederica (later Catherine the Great), daughter of Christian August, Prince of Anhalt-Zerbst and Johanna Elisabeth of Holstein-Gottorp. The young princess formally converted to Russian Orthodoxy and took the name Ekaterina Alexeievna (i.e., Catherine). They married on 21 August 1745. The marriage was not a happy one but produced one son, the future Emperor Paul, and one daughter, Anna Petrovna (20 December 1757 – 19 March 1759). Catherine later claimed that Paul was not fathered by Peter: that, in fact, they had never consummated the marriage. During the sixteen years of their residence in Oranienbaum, Catherine took numerous lovers, while her husband did the same in the beginning.
Henry III of Castile
On 17 September 1388, Henry married Catherine of Lancaster (1372–1418), the daughter of John of Gaunt, 1st Duke of Lancaster, and Constance of Castile, who was the elder daughter of King Peter. This ended a dynastic conflict and solidified the House of Trastamara. Their marriage ceremony took place in Palencia Cathedral and they had three children: