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William was a Duch Prince and the Royal House of the Netherlands is the House of Oranje (Orange) - so it refers to his Dutch Royal nationality
Queen Beatrix of Netherlands' Heir is her son Willem-Alexander, Prince of Orange
The leader was William of Orange, also known as William the Silent or as Prince William I of Orange. He was born in 1533 and was assassinated in 1584 by Balthasar Gerard. His heirs form the monarchy in the Netherlands to this very day.
Prince Alexander of the Netherlands died on 1848-02-20.
Prince Bernhard of the Netherlands was born on June 29, 1911.
Prince Maurits of the Netherlands was born on April 17, 1968.
Prince Maurits of the Netherlands was born on April 17, 1968.
Prince Alexander of the Netherlands was born on 1818-08-02.
Prince Constantijn of the Netherlands was born on October 11, 1969.
Prince Maurice of the Netherlands was born on 1843-09-15.
Prince Ernest Casimir of the Netherlands died in 1822.