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 I of Russia
It is possible that Menshikov, who was quite jealous of Peter's attentions and knew his tastes, wanted to procure a mistress on whom he could rely. In any case, in 1703, while visiting Menshikov at his home, Peter met Marta. In 1704, she was well established in the Tsar's household as his mistress, and gave birth to a son, Peter. In 1705, she converted to Orthodoxy and took the new name of Catherine Alexeyevna ("Yekaterina Alexeyevna"). She and Darya Menshikova accompanied Peter and Menshikov on their military excursions.