List of royal marriages to commoners

Royal marriages to commoners have historically been uncommon, due to traditions of members of royal families, especially high-level ones, only marrying other persons considered to be royalty, sometimes with penalties for royals who married far below their rank, deemed morganatic marriage. Often, alliances could be created between countries or strengthened within a country through intermarriage of two royal families.

Source: Wikipedia — List of royal marriages to commoners (CC BY-SA 4.0)