Was the House of Orange considered 'Royal' enough? I mean I'll be the first to admit that I don't know much about early Dutch history but the House of Orange wasn't considered a real reigning House until William III and even then there was times that their rule was threatened internally. Until William II of Orange's marriage to Princess Royal Mary none of the major Houses married into or out of the House of Orange.
Hm. I think that the Principality of Orange itself didn't really count, being by that time merely nominal and not, I think, held immediately (might be wrong on that though) . Nor did the Dutch headship of state, because the Staatholdership was elective. But, the House of Orange also held their hereditary domain of Nassau-Dillenburg, which was am Imperial county and therefore a ruling house . That was quite respectable, though not very rich. But German protocol and precedence is inhumanly complex.