Peter the Great was Tzar of Russia, and ruler of an enormous and powerful empire. After an unsuccessful first marriage, he had had his first wife forced into a convent in order to rid himself of her. Even then, it was almost impossible to imagine royalty marrying a commoner, yet that is exactly what Peter did with his second wife.
It is said that he came across the future Catherine I, Marta Elena Skavronska, while visiting the household of Prince Alexander Menshikov, where she labored. He fell in love with this peasant woman, and raised her to royalty. They secretly married in 1707, and it was her children who continued the royal line of Russia. In 1724, a year before Peter’s death, he even named her co-ruler of the Russian Empire, making her the first female ruler of Russia.