Through his father, a member of the House of Amsberg, he is descended from families of the lower German nobility, and through his mother, from several royal German/Dutch families such as the House of Lippe, Mecklenburg-Schwerin, the House of Orange-Nassau, Waldeck and Pyrmont, and the House of Hohenzollern.
Willem-Alexander Claus George Ferdinand was born on 27 April 1967 in the Utrecht University Hospital, Now the University Medical Center Utrecht in Utrecht, Netherlands. He is the first child of Princess Beatrix and Prince Claus, and the first grandchild of Queen Juliana and Prince Bernhard. He was the first male Dutch royal baby since the birth of Prince Alexander in 1851, and the first immediate male heir since Alexander's death in 1884.
He is descended from the first King of the Netherlands, William I of the Netherlands, who was also a ruler in Luxembourg and several German states, and all subsequent Dutch monarchs. By his mother, Willem-Alexander also descended from Paul I of Russia and thus from German princess Catherine the Great. Through his father, he is also descended from several Dutch/Flemish families who left the Low Countries during Spanish rule, such as the Berenbergs. His paternal great-great-grandfather Gabriel von Amsberg (1822–1895), a Major-General of Mecklenburg, was recognized as noble as late as 1891, the family having adopted the "von" in 1795.
King Willem-Alexander is a descendant of King George II and more relevant for his succession rights of his granddaughter Princess Augusta of Great Britain. Under the British Act of Settlement, King Willem-Alexander temporarily forfeited his (distant) succession rights to the throne of the United Kingdom by marrying a Roman Catholic. This right has since been restored in 2015 under the Succession to the Crown Act 2013.