SOURCES: LDS FHL AF # 4H26 - SB (familysearch.org)
"Ancestors/Descendants of Royal Lines" (Contributors: 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>, L. Orlandini, 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... http://geneastar.org.
NOTE: From the information I have gathered so far, either William had two marriages, or Agnes (or Jane) Launcelyn and Agnes Wydeville were one and the same. The William Dormer with each source has the same birth and death years. I have attached Agnes Dormer to parents William Dormer and Jane Launcelyn, as shown on LDS familysearch.org and treated this as William having had two wives. THIS IS A TENTATIVE PLACEMENT.