Following is excerpted from a posting by Douglas Richardson to soc.genealogy.medieval, newsgroup:
From: Douglas Richardson (royalancestry@@msn.com)
Subject: Joan, 1st wife of Sir Edmund de Mortimer (died 1304)
Newsgroups: soc.genealogy.medieval
Date: 2002-01-13 02:22:43 PST
Dear Newsgroup ~
I recently came across four legal cases in the Year Books of King Edward I which appear to identify the hitherto unidentified first wife of Sir Edmund de Mortimer (died 1302), of Wigmore, co. Hereford. The unknown first wife is thought to have been the mother of Sir Edmund's daughter, Iseult de Mortimer, wife of Hugh de Audley, from whom many colonial immigrants are descended.
Although the particulars provided in the legal cases are less than desireable, the first legal case presented below indicates that Sir Edmund's wife's name was Joan. A pedigree is set forth in which Joan is identified as the daughter of Maud, who in turn is said to be the daughter of "W.", which "W." was in turn called brother and heir of Henry.
Curiously, the wording of the pedigree in the first Mortimer case seems to be a near exact match to two other suits in the same Hereford iter which involve property held by Sir Reynold de Grey, of Wilton, co. Hereford, and his wife, Maud de Longchamp. In one of these suits, Maud de Longchamp is identified as the daughter of "W.", which "W." in turn is identified as the brother and heir of a certain Henry. In both the Mortimer and Grey cases, the said "Henry" is stated to have received his lands by grant of King Richard. In the Mortimer suit, the King demands the manor of "C." against Edmund de Mortimer and Joan his wife. The Prior of "E." is said to hold the advowson. In one of the Grey suits, the king demands the manor of "C." against Reynold and Maud de Grey, the advowson of which property is held by the Prior of "C."
Since the particulars in the Mortimer and Grey suits are similar in virtually every point, it seems highly probable that Sir Edmund de Mortimer's wife, Joan, is in fact the daughter of Sir Reynold de Grey and his wife, Maud de Longchamp.
The chronology seems to work o.k. for this identification of Edmund de Mortimer's wife. Research indicates that Edmund de Mortimer was born about 1252, being aged 30 at his father's death in 1282. Sir Reynold de Grey was born say 1230/5, and married before 1257 to Maud de Longchamp, the heiress of Wilton, co. Hereford. As such, it seems entirely possible that Sir Edmund de Mortimer's wife, Joan, was the daughter of Sir Reynold de Grey.