I see what you mean, Marc. But compared to Catherine, who adapted the lifestyle of the country she ruled over and where she spent the most time of her life, Princess Michael is at least half Austrian-Hungarian, was raised by her Austrian-Hungarian mother and speaks German with an unmistakable Austrian accent. As her father was foremost Silesian it is not that easy to call them German IMO. I do know Silesians myself and I can assure that they first of all consider themselves Silesian and not German or Polish (which is, BTW, difficult for Silesians, as they aren't seen as Germans in Germany or Poles in Poland either). I'm not an expert when it comes to Silesia, but its history is difficult. I know that one of Princess Michael's biographies stated that she is in fact only one quarter German (dunno if that's correct) and in this interview she more or less says that her father's Silesia was the one who was part of the Austrian-Hungarian Empire:
BBC - BBC Radio 4 Programmes - Desert Island Discs, HRH Princess Michael of Kent
It's an interesting interview by the way - a 40 minutes conversation.
It's all pretty tricky I think. I come from a part of Germany where most people feel more French than German (and by blood we are more French/Celtic for sure), yet, through political decisions, we belong to Germany now, speak German and count as German.
I'm not sure, but I believe that Günther von Reibnitz' first language must have been German. People from that area in Silesia also spoke a dialect, known as "wasserpolnisch" (a mixture between Polish, Czech and German). His background and family history are quite complicated - wasn't his German maternal grandmother in fact Jewish? One of the bios says that Ida Crone, who married von Reibnitz' maternal grandfather, was Jewish...