Frederick Nassau de Zuylestein (1608-1672) was an illegitimate son of Frederick Henry, Prince of Orange. Frederick Henry, or Frederik Hendrik in Dutch ( 29 January 1584 – 14 March 1647) was the Prince of Orange In 1659, he was made governor of the household of his nephew, William III of Orange. William III or William of Orange (14 November 1650 &ndash 8 March 1702 He is informally known in Northern Ireland and Scotland as "King Billy" He was married to an Englishwoman, Mary Killegrew, and was dismissed in 1666 under suspicion of pro-English leanings. His son, William, later became a close confidant of William III.