Well, I dont know about the others, but the Duke and Duchess of Braganza are considered very close cousins of Luxembourg Granducal Family, after all they have a lot of Braganza blood pretty much from all branches...
And I am being mean here...the Parmas on the B list... perhaps a small "revenge"? We know that the late Duke of Parma was "not amused" at Prince Henri marriage with Miss Maria Teresa Mestre Y Baptista...
--Previous Message-- : The A and the B list intrigue me. The Duke and : Duchess of Bragança, the Prince and Princess : of Piemonte, Prince Alexander and Princess : Katherine of Serbia, Princess Margarita and : Prince Radu of Romania... all of them were : on the A-list. : : The Duke and Duchess of Parma (Chef of the : House Bourbon-Parma, of which Jean, Henri : and Guillaume consider themselves Princes : of) as well as Prince Georg-Friedrich and : Princess Sophie of Prussia were examples of : the royals on the B-list. : : I can not find a clear line in that policy. : The Chambre des Députés was a relatively : small banqueting venue, this caused these : somewhat painful divisions i.m.h.o. : : :