Do I add " ’s " after the number on a pope/king’s name? (e.g. Pope Paul VI’s)

Solution 1:

The English apostrophe-s is not a case inflection the way you have in German or Russian, Latin or Greek. Rather it is a clitic that attaches to the end of the entire noun phrase, not merely to the head noun of that phrase.

That's why you have things like the Queen of England’s hat on one hand or King Henry VIII’s many unfortunate wives on the other. Just to show you how far this can go, some people even find the man at the door’s voice perfectly fine. Some will even talk about my wife and I’s dinner, at least in speech.

This phenomenon is sometimes called the Saxon genitive, despite being neither Saxon nor genitive.