King and Peasant are two tricky words, the idea of a King wasn't what we would typically think of a King today. A king during this time (after the 'fall of Rome') was chosen and his authority was not absolute.

An example of this could be Clovis I, who many regard as the father of Europe. While he had some Roman Senatorial blood in his family, he wasn't descended from a line of Kings, per se. He was by no means what we today would consider a peasant though, he was from a wealthy family that had some influence in Roman Gaul. Clovis would eventually go on to claim the title of protector or supreme leader of what they considered to be the Western Empire of Rome, even though they were no longer 'in Rome'.

Sources: Gregory of Tours, History of the Franks Notker the Stammerer, Life of Charlemagne