William III, King of the Netherlands was the father of Queen Wilhelmina. He first married his first cousin Sophie of Wurttemberg and they had three sons who all died before King William. Queen Sophie died in 1877. William remarried in 1879, the much younger Princess Emma of Waldeck and Pyrmont who became the mother of Queen Wilhelmina.
Dutch monarchs and their heirs-Queen Wilhlemina with Crown Princess Juliana, then Crown Princess Juliana with Princess Beatrix, then Crown Princess Beatrix with Prince Willem-Alexander, then Crown Prince Willem-Alexander with Princess Catharina-Amalia