William de Warenne, Knight, son and heir of John de Warrenne and Alice de Lusignan, was born 15 Jan 1255/6 at Warren, Sussex, England.  He married Joan de Vere about 10 June 1285.  She is the daughter of Robert de Vere, Knight, and Alice de Sanford.  They had one son, John, and one daughter, Alice.  "Sir William was knighted at Winchester in 1285."  He was ambushed and slain by his rivals after a tournament at Croyden 15 Dec 1286. 
Note: William de Warenne, Knight, did not ever inherit the title of Earl of Surrey, because he died before his father. His father was the 7th Earl of Surrey and his son was the 8th Earl of Surrey.
Father: John DE WARENNE, 7th Earl of Surrey, b. abt. 1231, Warren, Sussex, England. d. abt. 1304
Mother: Alice (Lusignan) DE WARENNE, b. abt. 1224, of Arundel, Sussex, England. d. aft. 9 Feb 1256
Source: S150 Title: The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Volume: vols. I-XII Abbreviation: Complete Peerage Author: Cokayne, George Edward Publication: St. Catherine Press Ltd., London, 1910-1959
Source: S152 Title: Ancestral Roots of Sixty Colonists Who Came to New England between 1623 and 1650 Abbreviation: Ancestral Roots, 6th ed. Author: Weis, Frederick Lewis Publication: Genealogical Publishing Co., Inc., Baltimore, MD, 1988 Note: RIN#10004
Source S-923559106 Repository: #R-923559107 Title: Ancestry Family Trees, Publication: Online publication - Provo, UT, USA: The Generations Network. Original data: Family Tree files submitted by Ancestry members.
FamilySearch (TM) International Genealogical Index v5.0, Intellectual Reserve, Inc., (The Church of Jesus Christ of Latter-Day Saints http://www.familysearch.org), Film 458041 and Film: Batch F610715, Sheet 013, Source Call No. 1621473
It may be possible to confirm family relationships with William by comparing test results with other carriers of his Y-chromosome or his mother's mitochondrial DNA.
Y-chromosome DNA test-takers in his direct paternal line on WikiTree: