I know that there were similar divisions in European royal families over the Carlist controversy in Spain. In fact, that was the whole reason why the Spaniards opposed the marriage of Infanta Maria de las Mercedes to Prince Carlo of Bourbon-Two Sicilies: his father (Alfonso, Count of Caserta), along with a Parmesan cousin, had fought on behalf of Juan, Count of Montizón, in the Spanish succession war of the 19th century. In fact, there were demonstrations to protest the union.
But the son was not the same person as the father, and Queen Regent Maria Cristina wholeheartedly supported her new son-in-law (a first cousin, once removed) as he joined the royal family. The family of her brother, Archduke Friedrich, Duke of Teschen, largely supported the claim of Queen Isabel II on the throne of Spain. But some of his daughters married into royal families who supported the Carlist cause ...
It had to have been a messy situation elsewhere, with European royals divided over Carlism. Of course, that had nothing to do with a renunciation (like the Sicilian dispute) but rather, King Felipe V earlier trying to impose the Salic law on Spain -- notwithstanding the fact that he owed his claim on the throne to a woman.
It's interesting that the Count of Paris was a stickler for renunciations: perhaps it was because the Orléanists owed their position as French claimants to the Anjou renunciation. It's also interesting that later on, the Carlist faction in Spain was genealogically linked to the Legitimist cause in France. I believe that the house of Orléans have largely supported the claims of Queen Isabel II on the Spanish throne, as well as Queen Maria II on the Portuguese throne. Heck, some of the members have married descendants of these queens regnant ...
The Brazilian case is almost dead this days as none of D.Pedro's sons seems interested in carrying on their father's claim.
As to the TS claim many years ago the late Count of Paris criticized the support the Count of Barcelona gave to the Calabrias (continued by JC and F VI) with this sentence: My daughter is married to the duke of Calabria and yet I support the Castro branch.
And he justified : The duke of Caserta renounced his rights when he married Maria de las Mercedes. He had no right to renounce his renounciation. And he reminded Barcelona that the duke of Segovia might one day come back on his renounciation and leave D.Juan in a difficult situation.
Despite being married to Pss Isabel from the Petrópolis branch, Henri CoP also supported the Vassouras branch due to his respect for renounciations.
Once you renounce, it is for ever.
Are the Spanish royals the only ones who side with Prince Pedro, as head of the royal house of Bourbon-Two Sicilies? Do all the others
(in particular, the heads of the other houses) support Prince Carlo, the Duke of Castro? What do they think of him naming his elder daughter, Princess Maria Carolina, as heir?
What about the other divided houses? Is the claim of the Grand Duchess Maria Vladimirovna of Russia, as head of the Romanov imperial house, largely supported by others?
Or the Brazilian dispute? I know that there are quite a few contested claims in these non-reigning houses. It's understandable, since a dynasty cannot easily clarify the succession or change rules, after getting deposed. That's why once sees qualifiers and disclaimers such as "Archduke George of Austria is the only one of his parents' seven children to have married in accordance with existing Habsburg house laws ... he and his son would eventually succeed to headship, under the said laws ..."
What side do others take on the Austrian dispute, for that matter?