It seems there's a fair few current examples of sisters to monarchs/heirs that seem incredibly supportive and close to their sibling. For example:
Princess Anne
Princess Isabella
Princess Sofia of Spain
Princess Charlotte
Princess Maigret (Beatrix's sister).
Princess Benedikte
I wonder if there's some more historical examples of supportive sisters?
Just a small correction, Beatrix's younger sister, is named Margriet.
Which is the Dutch name for a daisey. Indeed a variant of Margaret and related.
Thank you, I do apologise! There's an old programme in the UK called Maigret which I must have been thinking of when I was typing.
I don't know much about Countess Mary, I did think of her when I wrote my post, but I don't know much about her supporting her brother.