Sir Edward de Warren, of Poynton - Ancestry of Edward - 2 generations missing

My source is "Plantagenet Ancestry" by Douglas Richardson, 2004. Edward is on page 752. His parents are John de Warenne, 8th Earl of Surrey (1286-1347) and his mistress Maud de Nerford. John's (8th Earl) parents are William de Warenne (1256-1286) and Joan de Vere. Then we get to William's parents, John de Warenne, 7th Earl of Surrey, and his wife Alice de Lusignan.