Prince and monarch aren't synonyms. A monarch isn't always a prince and a Prince isn't always a monarch. I'd imagine the same can be said of the others. Rulers would have been a better answer.

I can't comment on the other groups as it is an American grid and much of the references are lost on me. But regardless I would like more elaboration on the answers.

tiger not acceptable - gotta be tigers, stupid! And forget King, we want prince! Duh

Definitely should have accepted "rulers" which fit your category better than your answer did.

utterly hopeless definitions sadly