Robert FitzHamon, probably born in the 1040s or 1050s, was the son of Hamo Dapifer the Sheriff of Kent and grandson of Hamon Dentatus ('The Betoothed or Toothy', i.e., probably buck-toothed). His grandfather held the lordships of Torigny, Creully, Mézy, and Evrecy in Normandy, but following his death at the Battle of Val-ès-Dunes in 1047, the family might have lost these lordships. He is said to have been a relative of William the Conqueror, but the nature of the relationship is unknown.