William FitzWilliam

William FitzWilliam (19 December 1479 – June 1543) was the illegitimate son of William, Prince of Wales, later William III of England and France.

Upon his father's accession to the throne, he was formally ennobled as the 1st Earl of Durham in 1472, granted three estates in County Durham and Berkshire. He married Margaret de Bohun, the daughter of Everard de Bohun, Lord Protector of England during the 1472 interregnum. Her dowry totalled to £3,000 as well as several cottages in the Lake District, making William one of the wealthiest northern nobles of the age. With Margaret, he had three children:
 * Roberta FitzWilliam, Countess of Northumberland (1489 – 1555)
 * William FitzWilliam, 2nd Earl of Durham (1492 – 1560)
 * Everard FitzWilliam, 2nd Baron Hungerford (1496 – 1552)