Who does each of the four kings represent in a deck of playing cards?

Each of the four kings in a pack of playing cards as used in games like poker represent a real king from word history. Here are the kings of each of the four suits and the royal leader they represent:

Diamonds – Julius Caesar, Rome.

Clubs – Alexander The Great, Macedon in Greece.

Hearts – Charles The Great, Carolingian Empire.

Spades – King David, United Kingdom of Israel.