Princess Caroline & Prince Ernst August — 21 Years

Princess Caroline is best known for being the eldest child of the American actress by the name of Grace Kelly and Rainier III, Prince of Monaco. Before Princess Gabriella and Prince Jacques were born, Caroline had been entitled to inherit the throne of Monaco.

Caroline got married to Prince Ernst August in 1999, and even though they have been together for about 21 years, the relationship between the two of them is quite complicated, to say the least. Also, according to Daily Mail, Prince Ernst has been spotted with another woman, so we have to wonder about the future for these two.