Each king that you see on a set of playing cards did actually exist, and has a historical background. The King of Spades is King David, found in the Bible. The King of Clubs was Alexander the Great, of Macedonia. The King of Hearts was Charlemagne, the Emperor Charles the Great, and the King of Diamonds was Julius Caesar the great Roman Emperor.
A note about comments and e-mails: A few people write comments at the end of a particular blog. They are always welcome, and I look forward to them. However, your e-mail does not appear, and so if someone asks a question, I cannot answer you, unless I know your e-mail. So what I would suggest is that, besides your comment, drop me an e-mail also at this address firstname.lastname@example.org I always welcome e-mails and respond to them instantly.