With a little bit of goodwill, Pr. Henry of Battenberg might fall in your example.
He was a foreign prince "forced" to expatriate and take exile in the UK by Q.Victoria as a condition for her to give her amen to his wedding to Pss.Beatrice, a royal princess who never succeeded, despite having rights to the throne.
He was of royalish ascendance and in line for the succession to the Battenberg (nominal) principality.
Despite being issued from a morganatic marriage in his own country, Queen Victoria considered him equal enough to marry her youngest daughter.
And with his marriage came the british nationality and the title of HRH (as you seek) in his adoptive country, granted from the Queen.
I know that the Spanish (e.g. Castile, Aragon, Leon, and Navarre) and Portuguese thrones have always permitted female succession (something the duke of Anjou, who became King Felipe V of Spain, had a hard time in understanding and accepting: he conveniently forgot that he had inherited the throne through his grandmother, Infanta Maria Teresa).
But until Isabel I of Castile, no woman actually ruled in her own right. Rather, women would inherit thrones and become nominal queens regnant, while their husbands would rule in their stead (Fernando II of Aragon had his own domain, so there was no need for him to bother with that of his wife). As such, the said husbands were rightly styled as kings -- not just kings consort. The latter custom was a later evolution (e.g. Francisco d'Asis of Spain, Ferdinand of Portugal).
What I've been wondering about are those royal princes who were husbands of princesses who never succeeded, despite having rights to thrones -- such as the sons-in-law of King Alfonso XII of Spain. Both were foreign princes of equal birth who settled in the native lands of their wives, and were accorded Spanish royal titles (evidently it's possible to create someone into an Infante of Spain).
Has it generally been the custom throughout European history, that an equally born husband of a princess with succession rights who settles in her country is granted a royal title there? I know that there probably haven't been many examples, since most thrones have barred females altogether, or granted them only limited rights. The Romanov imperial succession, for instance, operated under the semi-Salic law: to the best of my knowledge, not even the dukes of Oldenburg who settled in Russia, after marrying grand duchesses or princesses there, were accorded Russian royal titles. Correct me if I'm wrong ...
Well, even a member of a deposed house is still a royal, and Emperor Franz Joseph of Austria was known to lend a hand of hospitality to the exiled members of the Parmesan and Sicilian dynasties -- some of whom settled in his empire, and even married into the Habsburg imperial house as *equals*.
As it was, the two eldest sons of Alfonso, Count of Caserta, who in 1894 succeeded his older half-brother (Francesco II, the last king) as head of the royal house of Bourbon- Two Sicilies, settled in Bavaria and Spain, respectively. The elder one, Ferdinando Pio, the Duke of Calabria, married in 1897 Princess Maria Ludwiga -- a granddaughter of Prince Regent Luitpold and daughter of the future King Ludwig III -- but was never granted a Bavarian royal title, despite settling in his wife's native land (where he eventually died and was buried).
But the younger one, Carlo, was created into an Infante of Spain after marrying her half-cousin, Infanta Maria de las Mercedes, and renouncing his Sicilian succession rights (with dire consequences for their descendants). I believe that he was not the first prince of Bourbon-Two Sicilies to be thus honored: in the previous generation, Queen Isabel II likewise created one of her own sons-in-law into an Infante of Spain. And Maria Ludwiga's cousin, Prince Ferdinand of Bavaria, also received this title after marrying Maria de las Mercedes' younger sister, Infanta Maria Teresa.
A more recent example of an equally born husband who is an exiled member of a deposed foreign dynasty settling in his wife's native land would be Archduke Lorenz of Austria-Este: he, too, was eventually accorded a royal title in her country (after Parliament changed the succession law). His father-in-law (King Albert II of the Belgians) declared him a prince of Belgium in 1995.
Are there other examples? And am I correct that this has generally been the custom for royal husbands of princesses with succession rights, who expatriate themselves and settle in their wives' native lands?
I personally think it would have been lovely if the Duke of Calabria (who eventually became the titular King Ferdinando III of the Two Sicilies) could have been granted the title Prince of Bavaria. But then, the German and Spanish kingdoms operated under different succession laws, so perhaps the difference in customs was understandable.