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
King Augustus III of Poland died in 1763, so Poland needed to elect a new ruler. Catherine supported Poniatowski as a candidate to become the next king. She sent the Russian army into Poland to avoid possible disputes. Russia invaded Poland on 26 August 1764, threatening to fight, and imposing Poniatowski as king. Poniatowski accepted the throne, and thereby put himself under Catherine's control. News of Catherine's plan spread and Frederick II (others say the Ottoman sultan) warned her that if she tried to conquer Poland by marrying Poniatowski, all of Europe would oppose her. She had no intention of marrying him, having already given birth to Orlov's child and to the Grand Duke Paul by then. She told Poniatowski to marry someone else to remove all suspicion. Poniatowski refused.