At the fuenral of Grand Duke Jean on May the different members of the royal houses came in order after the lenght of the reign with the longest reigning last. And bgefore it was also divided first the junior members, the the heirs and the the Head of 'States. And among these first Monaco and Liechtenstein who are HSH and the the royal Houses.
It would appear that those of princely rank are treated differently. I presume this has to do with the history of especially the German speaking lands where there were so many different types of rulers. I wonder are the mediatized houses ranked differently.
Unfortunately I do not read German (a little French) but I wonder if there are sources on this.