I think we need to distinguish between titles that are legally held and recognized by the State verses titles held in pretense. Elizabeth II is a prime example. Yes genealogically she is from the Wettin Dynasty and the collateral branch of House of Saxe-Coburg-Gotha. However, the British Royal Family did relinquish their German titles as you know, and plus the monarchy in Germany has been abolished so where is the legality of these titles stem from?
Concerning the foreign titles that descend from the Duke of Edinburgh, he did also relinquish his titles and the Greek monarchy has been abolished so where is the legal authority for those titles? Plus, In July 1930, the George V made the decision: the use of foreign titles by British Subjects was abolished and that no further recommendations for Royal Licences were to be submitted to him.
Continuing with the thread on in-house unions: do, in fact, the Belgian royals in male-line descent from King Leopold I have multiple titles? Is Elisabeth a princess of Saxe-Coburg and Gotha, in addition to being the crown princess of Belgium and the Duchess of Brabant? If so, then perhaps it would count as one of those situations of unused titles (which I previously brought up): one might be A prince(ss) of a country X, but never called that.
Yes, they are members of the Saxon princely house. Recently, the King brought back the inescutcheon of Saxony to the Belgian royal arms as well as the name Saxe-Coburg & Gotha; this, I feel, is in preparation to limit the Belgian princely title but still have a royal name for more distant members of the family.
Certainly nobody would ever call, right in Her Majesty's hearing, Queen Elizabeth II of Great Britain as a princess of Saxe-Coburg and Gotha ...
Her Majesty the Queen is still a member of the Saxon princely house, despite what her grandfather may have wanted. He was not ever head of the ducal line of Saxe-Coburg and Gotha nor did he have Saxon dynastic jurisdiction over members of his family. All his proclamation technically amounted to is disallowing use of those titles in his realms (no matter how it was worded).
One presumes that people would be less hesitant about referring to her children as princes and princess of Denmark ...
Right; the Duke of Edinburgh basically renounced the use of his dynastic titles, which still descend (disused) to his legitimate male line descendants... Prince of Greece and of Denmark; Duke of Schleswig, of Holstein, of Stormarn, of Dithmarschen, of Lauenburg, and of Oldenburg... maybe also Prince of Glücksburg if that Danish title wasn’t extinguished in that line when Christian IX became king.
Now to be sure, the Greek royals from King George I on have always styled themselves a princes and princesses of Denmark; but not the Norwegian royals. Swedish royals were also princes and princesses of Norway, until the person union between the two countries ended in 1905.
Norway for a long time was either under the yoke of Sweden or Denmark so it was important that they did not use their Danish titles.
The Dutch royals are also princes and princesses of Orange-Nassau -- correct?
There are no Princes of the Netherlands who are not also Princes of Orange-Nassau, so I would not consider this a “dual house” situation...
But members of the grand duchy of Luxembourg, although princes and princesses of Nassau-Weilburg until the deaths of all six daughters of Grand Duke Guillaume IV, are not styled as princes and princesses of Bourbon-Parma ... Or are they? I heard that they were, until the marriage in 1981 of Grand Duke Henri (then heir to the throne) to Maria Teresa Mestre. The then-head of the house of Bourbon-Parma did not approve the marriage. So Grand Duke Jean severed all ties to this dynasty. Is this correct?
That’s what the late grand duke wanted to do but he could not extinguish his descendants’ membership and any residual rights they may have had in the Houses of Bourbon/France, Spain, Etruria, and Parma (just to list them all!).
As for some of the non-reigning houses: what about the Bulgarian royals? Have they been styled as princes and princesses of Saxe-Coburg and Gotha? I know that the children of Queen Maria II of Portugal were, in addition to being Infantes and Infantas of Portugal, princes and princesses of Coburg, as well as dukes and duchesses of Saxony.
Not sure if they are specifically styled as such but they used the arms of Saxony and are members of the Saxon princely house.
Matters are interesting in Spain and Portugal, which have always honored the maternal heritage: one can also be an Infante/Infanta of Spain through his mother. Such was the case with the children of Maria de las Mercedes (elder daughter of King Alfonso II of Spain), who were also princes of princess of Bourbon-Two Sicilies. Similarly, the children of her younger sister (Maria Teresa) were Infantes and Infantas of Spain, as well as princes and princesses of Bavaria. The latter titles, of course, were forfeited when their father (Prince Ferdinand of Bavaria) renounced in 1914 his Bavarian royal titles and succession rights to the kingdom.
These female line titles were always specially created or decreed and not automatic. I am not so sure that the Bavarian titles were actually alienable.
But as for the Romanian royals, I'm not sure if they've been styled as princes and princesses of Hohenzollern-Sigmaringen ... I have no doubt that that's what they were/are; but I'm not sure if they've actually used these titles.
They certainly have the titles because King Michael explicitly renounced their use.
Since the house name of the Brazilian dynasty got hyphenated to Orléans-Braganza, it goes without saying that the princes and princesses of Brazil (i.e. those descended from Isabel) have also been princes and princesses of Orléans -- correct? Or perhaps I'm mistaken, and they haven't used their French royal titles. Perhaps calling oneself a Prince(ss) of Orléans-Braganza is a way of simplifying things ...
The hyphen is a simplification, they are actually Princes of Orléans *and* Braganza.