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 Jagiellon
Catherine was crowned queen of Sweden in the spring of 1569. Her relationship with John III continued to be very good during her lifetime, and there are no extramarital partners known on either side. She had her own Catholic chapel and her own Catholic staff, among them several Catholic monks and priests, which shocked the Protestants. Her court was headed by Karin Gyllenstierna. As a person, it does not seem to be much slander about her. Her fervent Protestant brother-in-law, the future Charles IX mentioned her in his chronicle when he described King John: "His Princess was full of virtue and piety, still her faith did come from Rome".