Puzzling Principles on Princes and Princesses

There are Princes and Princesses, and then there are Princes and Princesses. The problem lies in where they come from; the title of Prince does not mean the same thing depending on where it comes from. The puzzle is solvable, given some knowledge of geography and history. And some of the muddle derived from translating foreign titles into English. 

Pierre Casiraghi of Monaco