William Fitzwilliam 
William was born about 1608. William's father is Thomas Fitzwilliam and his mother is Margaret Plunkett. His paternal grandparents are RIchard Fitzwilliam and Jane Preston. He was an only child. He died before 1681.General Notes
3rd Viscount Fitzwilliam of Merrion
SOURCES: LDS FHL Ancestral File # (familysearch.org)
WEB:
"Ancestors/Descendants of Royal Lines" (Contributors: F. L. Jacquier (History of Charlemagne by Christian Settipani); L. Orlandini, Manuel Abranches de Soveral, Reynaud de Paysac, F.L. J P de Palmas (Aurejac et Tournemire; Frankish line; The Complete Peerage}, Jacquier (Genealogy of Lewis Carroll, Justin Swanstrom, The Royal Families of England Scotland & Wales by Burkes Peerage; Debrett's Peerage & Baronage; Table of descendants French Canadian Genealogical Society; Families of Monfort-sur-Risle & Bertrand de Bricquebec; The Dukes of Normandy, XXXXI), A. Brabant ("Dynastie Montmorency, Michel d'Herbigny), Paul Leportier, Claude Barret, H.R. Moser (Burke Peerage), O.Guionneau, L.B. de Rouge, E. Polti, N. Danican (Britain's Royal Families; Buthlaw, Succession of Strathclyde, the Armorial 1961-62) A.Terlinden (Genealogy of the existing British Peerage, 1842), L. Gustavsson, C. Cheneaux, E. Lodge, S. Bontron (Brian Tompsett), R. Dewkinandan, H. de la Villarmois, C. Donadello; Scevole de Livonniere, H. de la Villarmois, I. Flatmoen, P. Ract Madoux (History of Morhange; Leon Maujean; Annuaire de Lorraine, 1926; La Galissonniere: Elections d'Arques et Rouen), Jean de Villoutreys (ref: Georges Poull), E. Wilkerson-Theaux (Laura Little), O. Auffray, A. Brabant (Genealogy of Chauvigny of Blot from "Chanoine Prevost Archiviste du Diocese de Troyes Union Typographique Domois Cote-d'Or 1925), Emmanuel Arminjon (E Levi-Provencal Histoire de l'Espagne Andalouse), Y. Gazagnes-Gazanhe, R. Sekulovich and J.P. de Palmas ("notes pierfit et iconographie Insecula", Tournemire), H de Riberolles (Base Tournemire), Franck Veillon; ,(Histoire Généalogique de la Maison de Hornes, Bruxelles 1848; Notice Historique Sur L'Ancien Comté de Hornes, Gand 1850; Europäische Stammtafeln, Marburg 1978); E.Driant / "La Maison de Damas" par Hubert Lamant, 1977 (Bibliothèque municipale d'Eaubonne)
........... http://geneastar.org.
They had a son named Thomas.