William FitzWilliam, 3rd Baron of Halton, 3rd Constable of Cheshire was born on an unknown date to William FitzNigel (-1134) and Agnes de Gant (-c1134) and died 1149 Normandy, France of unspecified causes.
"William constable of Cheshire, junior, son of William, was the third baron of Halton.
He removed the canons of Runcorn to Norton.....He gave also half of Raby in Wirrall to the abby of St. Werburge in Chester......This William is stiled nepos Walteri de Gant, and his sister Agnes stiled Agnes de Gant. By which it may seem that William son of Nigell married a sister of Walter de Gant, and daughter of Gilbert.
This William constable junior, died in Normandy in the reign of king Stephen without issue; and so his inheritance was divided and shared between his two sisters and heirs."
--The History of the County Palatine and City of Chester: Comp. from Original Evidences in Public Offices, the Harleian and Cottonian Mss., Parochial Registers, Private Muniments, Unpublished Ms. Collections of Successive Cheshire Antiquaries, and a Personal Survey of Every Township in the County; Incorporated with a Republication of King's Vale Royal and Leycester's Cheshire Antiquities, Volume 1 by George Ormerod, Daniel King, William Smith, William Webb (sheriff.), Sir Peter Leycester
Siblings
| Name | Birth | Death | Joined with |
| Agnes FitzWilliam (-c1157) | 1157 | Eustace FitzJohn (-1157) | |
| Leuca FitzWilliam (-c1162) | 1130 England | 1162 England | Robert de Mohaut (-1162) |
| Matilda FitzWilliam | |||
| William FitzWilliam (-1149) | 1149 Normandy, France | ||