"Proceedings of Somerset Arch. & Natural History
Society, 44 (1898): 209-210 states there can be "no doubt" that Thomas
d'Arderne, who married Lucy de Say, was the father of Ralph d'Arderne,
of Essex, who inherited Lucy's lands at Yeovil, Somerset. Ralph
d'Arderne, of Essex, was succeeded by a son and heir, Thomas, who
occurs in 1294."
It appears that there was a different Ralph d'Arderne who married Isabella Mortimer, per this other 2010 post at the gen.medieval forum.
WikiTree profile Arderne-30 created through the import of YOUNG.ged on Jul 12, 2011 by Zak Young. See the Changes page for the details of edits by Zak and others.
WikiTree profile DeArderne-31 created through the import of WILLIAMS 2011.GED on Jun 22, 2011 by Ted Williams. See the Changes page for the details of edits by Ted and others.
Source: S004444 Title: Ancestry Family Trees Publication: Online publication - Provo, UT, USA: Ancestry.com. Original data: Family Tree files submitted by Ancestry members. Note: #NS044441 Repository: Note: #NS044443