Is Cecilia de Arderne the same person as Cicily or Cecilia of Mercia, wife of Siward de Arden (b. c. 1075), who is son of Thorkell of Arden (d. c. 1100)? This site shows Siward de Ardennes as son of Turchil (from Warwickshire), which I believe is the same person as Thorkell. The alternate spelling for Thorkell are Thorkell or Turchil. Siward was his principal heir, according to Burke’s Peerage/Burke’s Landed Gentry, Volume I, 18th edition, by James Lees-Milne.