From what Robert has said, it looks to me as if royalty is in the blood. You are born royal or you are not.
One may marry into a royal house and have a title conferred upon them as in Diana, Princess of Wales, but Diana was never a royal princess and when she and Charles divorced, she was no longer Princess of Wales, she had never been "made royal". (Can that even be done??)
Even among royal families, only those born directly to someone who is royal are automatically royal and then only if the parents are married and married to someone of equal stature (that is why there were so many "morganatic" marriages whose offspring though partly royal could not inherit.) Otherwise all of the "bastards" who have been conceived over the centuries would be royal.
Nicholas lost his "royal prerogatives" when he abdicated, but he was still a Romanov and he was still royal (or actually imperial).
But it is far more confusing that that. What about those princes of lesser blood who were elected to the thrones of so many countries during the 19th century. They were indeed royal in their own countries but not an heir, yet they could be elected to a high position in another country and become the royalty of that country and then be actually, in order of precedence, higher than their sibling who was not yet a ruling monarch but still only an "heir".
And then there is the example of Alexandra and Dagmar of Denmark. Both married into ruling families and both were sisters in a ruling family, yet Dagmar would take precedence over Alexandra as Dagmar was now an Imperial Highness and Alexandra was a "Royal Highness". Alexandra would not be Imperial until Victoria became Empress of India and passed on the title to her son and heir.
And as to those "imperial" and/or "royal" titles that are so much in contention today. Most have been married so many times and divorced so many times to both royal and non royal spouses that the royal blood is so thinned that it is almost untraceable. Just the fact that these descendants of royalty married someone of "unequal status" takes their children out of the royal running.
With the exception of the current pretender to the non existent throne of Imperial Russia (who is actually not an exception because there is some discussion as to the equal status of spouses in this case, too) if any of the these royal title holders went to buy a cup of coffee at Starbucks, it would cost them about $4 USD, just like it would cost you and me. (Except that I don't drink coffee

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So I guess the definition of "true royalty" is one has to be born to parents who are of royal blood and who have married equally so that both sides are royal.
Can one become "un-royal"? I guess one can renounce one's royal rights and prerogatives, but one can do nothing about one's blood or one's blood relations. (And we all have that problem to some degree

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