I have a four year old daughter so I’m quickly becoming acquainted with every movie and cartoon recently made with the theme of a girl falling in love with a prince only to discover that the prince is required to marry a princess. But don’t worry; most often the girl turns out to be royalty herself, what are the chances?

Now I know that King Edward VIII abdicated to marry a non-royal, but that was more because his fiancée was unpopular rather than because such a marriage was illegal. My question for all you is do you know of historical examples of marriage between royal and non-royal being forbidden?

First of all I would imagine that most royal weddings, until recent times, were more or less arranged so there would be little need for such a law, besides who would pass and enforce such an edict any way. Secondly why should it be forbidden, I can imagine many examples where a marriage between a royal and a wealthy bourgeois would be an asset to both parties.

Before the twentieth century, I'd say that an arranged marriage was just as common as a romantically-based one, even more so the wealthier you get, with royal marriages often being crafted to strengthen alliances between nations, businesses, or families. The only case I could think of might be in India or China, because of India's distinctive caste system (though there was quite a bit of 'wiggle room' in it, too) and because China is, well, China; the upper classes spoke a completely different language than the lower being the best illustration. Though in that case, it would probably be a case of marriage between upper and lower class being denied, not necessarily on royal/non-royal grounds.

EDIT: In the early days of the Roman Republic, it was forbidden for Patricians to marry Plebians, though this later changed. I do not know if such a distinction existed during Rome's monarchial days as an Etruscan city-state.

I have a four year old daughter so I’m quickly becoming acquainted with every movie and cartoon recently made with the theme of a girl falling in love with a prince only to discover that the prince is required to marry a princess. But don’t worry; most often the girl turns out to be royalty herself, what are the chances?

This sort of plot device has a very ancient pedigree. Stories of young men who fell in love with virtuous but unmarriageable (on account of being poor, foreign, etc.) ladies are a staple of Attic New Comedy (3rd C. BC). invariably, the long-suffering young woman discovers some ancient noble ancestor or somesuch, and the happy couple are married at last.

I'd also imagine that more often than not royalty would marry for political convenience, and then take the women they truly love as mistresses.

Before the twentieth century, I'd say that an arranged marriage was just as common as a romantically-based one, even more so the wealthier you get, with royal marriages often being crafted to strengthen alliances between nations, businesses, or families. The only case I could think of might be in India or China, because of India's distinctive caste system (though there was quite a bit of 'wiggle room' in it, too) and because China is, well, China; the upper classes spoke a completely different language than the lower being the best illustration. Though in that case, it would probably be a case of marriage between upper and lower class being denied, not necessarily on royal/non-royal grounds.
In ancient China polygamy was standard. The masses of peasants were monogamous but that was by circumstance, not by decree. Upper class men (including royalty and especially royalty!) were usually bound to have an arranged first marriage to their 妻 (wife) for alliance purposes but afterwards they were free to choose and accumulate as many 妾 (concubines) as their rank would allow. Offspring from concubines, however, have a lower rank and for inheritance purposes the original wife's children will take priority.

In Japan, Princess Sayako Kuroda had to relinquish her royal title because she married a commoner, but she was allowed to. In fact, her family attended her wedding and she received a dowry of over a million dollars. The relinquishment of the title was a legal technicality.

Victor Emmanuel II of Italy married morganatically (http://en.wikipedia.org/wiki/Victor_Emmanuel_II_of_Italy#Family_and_children) a simple peasant, whom he loved all his life. There is a movement asking for them to be moved to the same tomb.

Thanks for your input, interesting responses. So I take it that, at least as far as Europe is concerned, it is pure plot device. Makes me wonder what else in The Island Princess isn't historically accurate. :D

I thought the reason Edward VIII had to abdicate was that Wallace Simpson was divorced, not that she was unpopular. Times change, fortunately!

Wasn't the divorce the reason she was unpopular?

I always thought it was about the divorce, mainly.

For a twist on the tale in the OP, check out Princess Stephanie of Monaco:
http://en.wikipedia.org/wiki/Princess_St%C3%A9phanie_of_Monaco#Relationships

I hope you took notes on all those. I'll be asking questions later.

The heir to the Spanish throne, Prince Felipe, is married to a commoner, a Spanish journalist named Letizia with a divorce to her name.

I can only assume that princesses would be in fairly short supply; any daughter of nobility should do the trick.

The heir to the Spanish throne, Prince Felipe, is married to a commoner, a Spanish journalist named Letizia with a divorce to her name.

Well, these days there's not much controversy about the matter any more. There was a bit of a deal about it here when our current king married a commoner back in the 1960s. His son (current crown prince) married not just a commoner, but a single mother with a party-girl past and an alcoholic father, and the only ones who got their panties in a twist were old people who will be dead and irrelevant before it's his turn to be king.

Originally, I suppose such matches were unheard-of because marriages among the ruling classes were a matter of building alliances and dynasties, and were therefore usually arranged (or at least had to be approved) by the fellow wearing the crown. As a king, you might marry your children off to foreign royalty or high nobility in order to build alliances, or to domestic nobility in order to cement loyalty, etc. You wouldn't want them to marry some nobody who couldn't bring an army in case of war, or access to a lucrative trade route, or whatever.