Thanks for the tone of your post, explaining your points. Once more, I do not challenge the status of the order and its Grand Master, but the original question was about European Royal Families and the Order and its GM are not included in that cathegory.
It is indeed correct that the Order of Malta was not listed in the first part of the more recent additions of the Gotha, but he was listed with all the other reigning princes in the late 18th when he was ruling Malta (not surprising, since his ambassadors took precedence ahead of those of Tuscany). But the concept of 1st, 2nd and 3rd parts was actually fairly late in the history of the Gotha and rather irregular as non-reigning branches of reigning houses were included. So, for example, in the 1820s Monaco appeared not in the first part with sovereigns, but in part 2, with the princely mediatised houses and also the junior line of Lorraine-Guise (the duc d'Elboeuf), the daughters of the last duke of Courland, Princes Odescalchi, etc but one could find the Minister of the Order of St John listed among other ambassadors and ministers to the countries where the Order was accredited. The GM of the Order of Malta is elected for life, like the Pope, and is listed as Prince and Grand Master in the 20th century editions among the states. He is a Prince of the Holy Roman Empire, of the Austrian Empire and was recognised as such by the Kingdom of Italy. Today the Order has reciprocal diplomatic relations with 107 states. So his "recognition" certainly counts for something.
The question was about royal families or royal Houses. I know about the order of Malta. There are no dynastic rights in the order. The Grand Master is elected. Not a hereditary monarchy. Not sure if it can be considered a monarch. Contrary to the Pope, the Grand Master is not listed in the first section of the Almanch de Gotha.
No reigning royal house has recognised the Borbon-Segovia line’s pretension to the French throne.
In 2000 Louis de Bourbon was made a Bailiff Grand Cross of Honour and Devotion of the Sovereign Military Order of Malta with the style "duc d'Anjou" by a reigning prince, the Prince and Grand Master of the Order of Malta. In 2016 his wife was made a Dame Grand Cross of Honour and Devotion (a rank to which she could claim no right by her birth and ancestry, but only on account of her marriage to the head of a royal house).
Has any reigning prince similarly honoured prince Jean d'Orléans - either with or without an Orléanist title?
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