Peter the Great has multiple famous examples. Alexander Menshikov was his close advisor and it is suggested by some historians that he was a stable boy as a child. Catherine I, Peter's wife and Empress after his death, was born Marta Helena Skowrońska and lived a life of poverty/peasantry/possibly slavery before becoming mistress to Peter.

Abram Gannibal was originally a slave purchased as a boy from Africa by Peter the Great, who recieved an education and became a military engineer/nobleman into the time of Elizabeth's rule if my memory serves correctly.

Scholars argue whether Daniel from the Book of Daniel in the Hebrew Bible was a real person or not, but his story certainly counts if so.