Perhaps the most eloquent example - the wedding of the King of Great Britain Edward VIII. This monarch literally shocked his subjects by marrying a woman who not only belonged to noble families, but also was a twice-divorced. When he was faced with a dilemma: either to abandon the marriage with his beloved, or lose the right to the throne, the king lost his title to his younger brother George.
Some memorable beautiful and tragic love story of Prince Rainier III of Monaco and American actress Grace Kelly. It was a very loving, friendly couple. The couple were inseparable 26 years, until the tragic death of Grace in a car accident, which occurred in 1982. The prince, who survived his wife of 23 years old, suffered a hard her death and never to marry.
In our time, such unequal marriages nobody will be shocked. Of course, not always august parents approve of the choice of his sons, princes, but if they show firmness, defending the right to a happy personal life, it comes to formal marriages. For example, Crown Prince Felipe, son of the Spanish King Juan Carlos and Queen Sofia, married journalist and Danish Crown Prince Frederik married with a private secretary.
Can there be such a happy unequal marriages? It depends on many factors. Of course, if in place industrious and good Cinderella (even naive and infinitely far from the court etiquette) would be prudent, cynical predator who needs a title chosen, marital happiness is hardly possible. If the chosen one will be the Prince of decent, kind girl who really liked him as a person and not as sovereigns, then such a marriage may well be strong and happy.