In a posting dated 12/17/17 Douglas Richardson writes that Isolde, wife of Walter de Balun and Hugh de Audley was the daughter of Roger Le Rus. In a 1289 Court of Common Pleas, Isolde, holder of the Manor of Eastington, the daughter of Roger le Rus, sued Reynold de Balun over rights to the manor. She is clearly identified as the daughter of Le Rus. If you can read latin here is the cited document: 
Married #1 Walter de Balun.
Ancestry.com: An article in the New England Historical and Genealogical Register, vol. 116: 16-7, gives Isolt as the daughter of Edmund de Mortimer, and this opinion has been followed by Weis/Sheppard/Faris in Ancestral Roots (9-30, 207-30) and by Faris in Plantagenet Ancestry (Audley 13). -- Christopher Nash
From VCH Worc (Arley): "It passed from Roger to his son Edmund in 1282 [CP V, 379], and was granted by the latter to his daughter Iseult and her first husband Walter de Balun for their lives. After Walter's death Iseult married Hugh de Audley, and on his forfeiture in 1322 the manor was granted by the King to Iseult [Cal. Close, 1323-7, p. 467], who held it until her death about 1339-40 [Abbrev.Rot.Orig. (Rec. Com.), ii, 130]. The reversion after her death, during the minority of Roger de Mortimer, had been granted in 1336 to William de Bohun, Earl of Northampton [Duchy of Lanc. Royal Chart., no. 277], who had married Elizabeth widow of Edmund de Mortimer, grandson of the Edmund who had granted the manor to Iseult. [Cal. Close, 1354-60, p. 271; CP V, 379]. Roger came of age about 1348, but Elizabeth held the manor until her death in 1356, when it passed to her son Roger [Cal. Close, 1354-60, p. 271], who had become Earl of March by the reversal of his grandfather's attainder in 1354 [CP V, 243]." -- Christopher Nash
My research indicates that Iseult and her first husband, Walter de Balun, received the grant of the manor of Arley, Staffordshire from Edmund de Mortimer for the term of their lives. The grant evidently took place in or before 1286, in which year I believe Walter de Balun died. In 1305, following Edmund de Mortimer's death, his widow, Margaret, sued Iseult and her second husband, Hugh de Audley, for dower in the manor. In 1325 Iseult paid a fine of 10 pounds to the King for having acquired the manor of Arley without license from the king [References: William Salt Arch. Soc., vol. 7, pp. 6,137-138,142; vol. 9, pg. 132]. In the various wrangling over this property, there is no indication that Iseult had the manor in free marriage, or any indication that she was related to Edmund de Mortimer. Indeed, the gift being for life is unusual, as marriage settlements were usually permanent gifts, not lifetime grants. I also find it unusual that if Edmund de Mortimer granted the manor to Iseult and Walter for their lives that his widow, Margaret, would later sue them for dower, especially if Iseult was Edmund's daughter. Reading the records on this matter, I'm frankly skeptical that Iseult de Audley was Edmund de Mortimer's daughter. -- Douglas Richardson, GEN-MEDIEVAL, 19 Jan 2002
My Mortimer family notes show that Edmund de Mortimer had an uncle, Hugh de Mortimer (died 1273) of Chelmarsh, who married Agatha de Ferrers (died 1306), daughter of William de Ferrers, 5th Earl of Derby. If Iseult de Audley was the child of Hugh and Agatha, it would give her grandson, Sir James de Audley, the needed links to both the Mortimer and Ferrers families. Also, it would solve the obvious chronology problem of Iseult being Edmund de Mortimer's daughter. -- Douglas Richardson, GEN-MEDIEVAL, 25 Jan 2002
Reviewing the chronological difficulties involved in this problem, it seems the best solution is to push Iseult back a generation and make her a daughter of Roger de Mortimer, Knt. (died 1282), by his wife, Maud de Brewes. While this arrangement would make Iseult's first husband, Walter de Balun, the same approximate age as her father, it fits the chronology much better than Iseult being a daughter in the next generation.
Place: Upper Arley, Kidderminster, Worcestershire, England
Daughter of Edmund de Mortimer and unknown mistress of Edmund de Mortimer
Wife of Walter de Balun, of Much Marcle and Hugh de Audley, Baron Audley
Mother of Hugh de Audley, 1st Earl of Gloucester; Nicholas Audley, 1st Lord Audley;
Neville and Margaret de Audley
Half sister of Matilda de Mortimer; Roger Mortimer, 1st Earl of March; Hugh 1290-1380 de Mortimer, Sir; Elizabeth de Mortimer; John de Mortimer and 4 others
Isolt de Mortimer was the daughter of Sir Edmund de Mortimer, 1st Lord Mortimer and Margaret de Fiennes.1,2 She married, firstly, Sir Walter de Balun before 1286/87.1 She married, secondly, Hugh Audley, 1st Lord Audley (of Stratton Audley), son of James of Aldithley and Ela Longespée, between 1288 and 7 January 1293.1 She died after 1336.1
Isolt de Mortimer was also known as Isolde de Mortimer.3 From before 1286/87, her married name became de Balun.1 From between 1288 and 7 January 1293, her married name became Audley.1 She brought her second husband the manors of Eastingdon, Gloucestershire and of THornbury, Herefordshire.1 As a result of her marriage, Isolt de Mortimer was styled as Lady Audley on 15 May 1321. On 12 April 1326 she had livery of the manor of Arley, Staffordshire.1
Children of Isolt de Mortimer and Hugh Audley, 1st Lord Audley (of Stratton Audley)
Sir James Audley+4 b. b 1289, d. b 1 Mar 1333/34
Hugh Audley, 1st and last Earl of Gloucester b. c 1289, d. 10 Nov 1347
Alice Audley b. c 1304, d. 12 Jan 1373/74
1. [S6] G.E. Cokayne; with Vicary Gibbs, H.A. Doubleday, Geoffrey H. White, Duncan Warrand and Lord Howard de Walden, editors, The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Extant, Extinct or Dormant, new ed., 13 volumes in 14 (1910-1959; reprint in 6 volumes, Gloucester, U.K.: Alan Sutton Publishing, 2000), volume I, page 347. Hereinafter cited as The Complete Peerage.
2. [S2] Peter W. Hammond, editor, The Complete Peerage or a History of the House of Lords and All its Members From the Earliest Times, Volume XIV: Addenda & Corrigenda (Stroud, Gloucestershire, U.K.: Sutton Publishing, 1998), page 52. Hereinafter cited as The Complete Peerage, Volume XIV.
3. [S125] Richard Glanville-Brown, online <e-mail address>, Richard Glanville-Brown (RR 2, Milton, Ontario, Canada), downloaded 17 August 2005.
4. [S6] Cokayne, and others, The Complete Peerage, volume I, page 348.
5. [S6] Cokayne, and others, The Complete Peerage, volume I, page 346.
Father Sir Roger de Mortimer, 6th Lord Wigmore, Constable of clun & Herford Castles b. c 1231, d. 27 Oct 1282
Mother Maud de Brewes b. c 1226, d. 16 Mar 1301
Isolde de Mortimer was born circa 1260 at of Eastington, Gloucestershire, Thornbury, Herefordshire, England; Her ancestry is uncertain.She married Sir Walter de Balun circa 1270; They had no issue. Isolde de Mortimer married Sir Hugh de Audley, Lord Audley, Constable of Montgomery Castle, Sheriff of Shropshire & Staffordshire, Justice of North Wales, son of Sir James de Audley, Sheriff of Shropshire and Staffordshire, Justiciar of Ireland, Keeper of Newcastle-upon-Lyme Castle and Ela Longespee, before 1292; They had 2 sons (Sir James; & Sir Hugh, Lord Audley, Earl of Gloucester) and 1 daughter (Alice, wife of Sir Ralph de Greystoke, 1st Lord Greystoke, & of Sir Ralph de Neville, 2nd Lord Neville of Raby). Isolde de Mortimer died circa 4 August 1338.
Sir Walter de Balun
Sir Hugh de Audley, Lord Audley, Constable of Montgomery Castle, Sheriff of Shropshire & Staffordshire, Justice of North Wales b. c 1267, d. c 1 Apr 1325
Sir James de Audley d. c 1 Mar 1334
Sir Hugh de Audley, Lord Audley, 8th Earl Gloucester, Sheriff of Rutland b. c 1289, d. 10 Nov 1347
Mortimer-608 and Mortimer-44 are not ready to be merged because: There is a note to people managing Mortimer -44 and to people using this profile to build their own trees: that there is conflicting evidence and no proof that the parents associated with this profile are correct. So an un-merged match may be wise even though the other profile deals with the other suggested parentage until the true facts can be ascertained.
I have done some cleaning up on this profile, but there are still two distinct Biographies. There are also many references to her unproven ancestry, but she is still attached to parents. I think at least her mother should be removed.
Mortimer-44 and Mortimer-608 appear to represent the same person because: According to the Medieval Lands Index, FMG, (http://fmg.ac/Projects/MedLands/ENGLISH%20NOBILITY%20MEDIEVAL2.htm#IsoltMortimerdiedafter1336) Isolde was the illegitimate daughter of Edmund Mortimer. "According to the Complete Peerage, Isolda was the daughter of Edmund Mortimer and his wife Margaret de Fiennes. However, this is chronologically impossible if Isolda gave birth to her son Hugh Audley in . It is therefore assumed that Isolt was Edmund Mortimer's illegitimate daughter, although no proof has been found that this is correct."
Please merge and detach mothers, with notes in Bio about possibilities.
As pointed out by J.W. Flank, Douglas Richardson has since changed his opinion, thinking that Iseult is a sister of Edmund, but I don't think that Iseult was born as early as Douglas is now thinking that she was born. The relationship between Edmund & Iseult is based on the fact that Edmund gave rights to Upper Arley to Iseult for the remainder of her life, but Edmund was renting Much Marcle from Iseult's 1st husband Walter Balun, and, when Walter died, Iseult claimed an interest in Much Marcle (probably dowry rights), so the transference of Upper Marcle to Iseult could have been a "business deal" between Edmund & Iseult to replace her dowry rights. I am keeping the ancestry as daughter of Hugh de Mortimer & Agatha de Ferrers until more information surfaces.
Her parentage is unknown. It has been discussed on Gen-Medieval for years but still remains undetermined. Per Jim Weber, who follows the discussions: Douglas Richardson in the following post to SGM, 25 Jan 2002, makes an argument that Isolde/Iseult was a daughter of Hugh de Mortimer & Agatha de Ferrers, instead of Edmund de Mortimer by his 1st wife (as CP & many other sources have it). Although her parents are still uncertain (no direct evidence), the case of her not being a daughter of Edmund (or at least a legitimate daughter) is strengthened by the fact that, according to a post by Paul Reed (see notes under Edmund), Edmund was a cleric in the church until Nov 1282, and is not likely to be father of Isolde (who was certainly born before then).