Some time ago, I started a thread on the subject of living royals related to the entire ALMANCH DE GOTHA. The one name I didn't bother to bring up, and which to the best of my knowledge nobody else mentioned, was this fellow.
What do you consider related and unrelated? Every single existing reigning and non-reigning European royal family (except for Montenegro!) in the Gotha have Frederick I, Margrave of Brandenburg-Ansbach and Sophia Jagiellon, Princess of Poland as their most recent known common ancestors, so they’re all related in the sense that they can be connected to one another genealogically.
But it struck me that he and his twin brothers (Philip and Alexander) might actually have the best claim to being related to all the European royals -- even better than the Duke of Apulia (son and heir of the Duke of Aosta). This might be true, despite having common (e.g. Aspasia Manos) and noble (e.g. Countess Elisabeth Dobrzensky of Dobrzenicz) ancestry, thanks to a couple of morganatic marriages.
After all, through their father (Crown Prince Alexander), they descend from Queen Victoria of Great Britain, King Christian IX of Denmark, Czar Alexander II of Russia, and the kings of Prussia: that would cover all the Protestant royals. Also through their father, they descend agnatically from the house of Karageorgevich in Serbia and cognatically from the house of Petrovich-Njegosh in Montenegro. That would cover all the Orthodox royals.
Through their mother (Princess Dona Maria da Glória of Orléans-Braganza), they descend from Princess Imperial Isabel of Brazil, King Louis-Philippe of the French through several lines, the kings of Bourbon-Two Sicilies, Holy Roman Emperor Leopold II through several lines, and King Fernando VII of Spain. That would cover all the Catholic royals.
It has been said that the Romanian princesses have strong claims to being related to the entire GOTHA. But because they are not directly descended from any Karageorgevich prince or king of Serbia or King Nikola of Montenegro, there are some missing links. The same can be said of the Duke of Aosta and his son.
By contrast, the sons of Crown Prince Alexander are related to all the Orthodox dynasties listed in the first section of the GOTHA -- excepting, of course, the deposed house of Obrenovich in Serbia. The Romanian and Bulgarian royals, despite being mostly Orthodox, belong to houses of foreign origin, later imported into their countries. But the said houses are genealogically Catholic or Protestant (like the Romanovs of Russia). As it is, the Serbian princes have ties to both the Hohenzollerns and Coburgs.
Is all this true? Does anybody else agree with me that Peter, Philip and Alexander are the European royals with the best claim to being related to everybody in the GOTHA?
The interesting thing about the Hereditary Prince of Yugoslavia and his brothers is that their direct maternal line is entirely Bourbon princesses who married Bourbon princes and kings for something like nine generations.