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.
Catherine of Lancaster
Queen Catherine was the daughter of John of Gaunt, 1st Duke of Lancaster, and his second wife, Constance of Castile (the daughter and heir of King Peter of Castile, who died at the hands of his half brother Henry II). She was born in Hertford Castle, her father's chief country home, on 31 March 1373. Catherine became Queen of Castile through her marriage to Henry III.