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 the Great
Sir Charles Hanbury Williams, the British ambassador to Russia, offered Stanisław Poniatowski a place in the embassy in return for gaining Catherine as an ally. Poniatowski, through his mother's side, came from the Czartoryski family, prominent members of the pro-Russian faction in Poland. Catherine, 26 years old and already married to the then-Grand Duke Peter for some 10 years, met the 22-year-old Poniatowski in 1755, therefore well before encountering the Orlov brothers. In 1757, Poniatowski served in the British forces during the Seven Years' War, thus severing close relationships with Catherine. She bore him a daughter named Anna Petrovna in December 1757 (not to be confused with Grand Duchess Anna Petrovna of Russia, the daughter of Peter I's second marriage).