iannis said:When King George I came to Greece, he renounced his rights to the danish throne and the term Schwlesing- Holstein- Sonderburg- Glucksburg, which was not even a surname of the danish royal family, but named the four regions the kingdom was made of.
Opponents of the ex king Constantine usually call him like that (Glucksburg) ironically.
It was a nickname reinvented by the greek 'Entente' supporters during the WW I, because it sounded more 'german', and that would make people feel disgust for the then neutral king Constantine I (grandfather of Constantine's)
Therefore members of the greek royal family do not have a last name
Wilhelm never renounced his right to the family name, which is why all of the subsequent princes & princesses of the Greek Royal House were also permitted to be styled "of Greece & Denmark". He did renounce his right, and those of his descendants, to the Danish throne, which was later codified by the Danish Parliament.
All of the Royal Houses have a dynastic reference, but royalty does not traditionally use a surname. They do not need one as they are royal and referred by their style and title.