There are so many names for the King and Queen I found so similar to each other. For example, king Henry IV, Charles XI, etc. Why did these kings choose these names?
There was never a monarch of medieval Europe. Rather, in the Middle Ages there many countries that were monarchies.
Many histories have the habit I consider loathesome of translating and modernizing many foreign and historical names, so that Johan, Jehan, Jean, Juan, and Giovanni all wind up "John."
When you see a long string of Kings Louis or Henry or George, it's usually a way of making a dynastic statement. As well, most did not choose their names: it's the one Mommy & Daddy gave them.
Source: Ingraham, People's Names