|SOME NOTES ON MEDIEVAL ENGLISH GENEALOGY|
Volume 5, page 400, note b:
This Ralph [FitzBernard], aged 13, 14, or 15 in 1259, was s. and h. of John fitz Bernard (who d. shortly before 30 Oct. 1259), by Joan (living 15 Feb. 1262/3), da. and coh. of Robert Aguillon (Ch. Inq.p.m., Hen. III, file 24, no. 3 : Patent Roll, 47 Hen. III, p.1, m.15 : &c.). John was s. and h. of Ralph fitz Bernard (who d. before 10 June 1238), by his 2nd wife, Joan.
It seems that Joan, the daughter and coheir of Robert Aguillon, by Margery his wife, was the wife of Ralph FitzBernard (who died before 10 June 1238), not the wife of his son John (who died shortly before 30 October 1259). It is unlikely that Joan, who survived Ralph, was the mother of his son John. The evidence is summarised below.
In Trinity 1239, Joan who was the wife of Ralph FitzBernard appears as one of the daughters of Margery, the sister of Idonea de Beche, daughter of William de Fresney [Curia Regis Rolls, vol.16, no 614]. Another daughter of Margery is named as Isabel (deceased, leaving a son Adam, a minor, the son of Robert de Cokefeud), and these two, together with Thomas de Poninges and Ela his wife, and Giles de Argenteam and Margery his wife, were summoned to answer with Idonea.
It appears that Joan, Isabel, Ela and Margery were the four daughters and coheirs of Robert Aguillon. There is much evidence that they were his heirs, and two of them are called his daughters by Complete Peerage - vol.1, p.196, says that Margery, the wife of Giles d'Argentine, was his daughter (without citing evidence), and vol.10, p.658, says that Ela, the wife of Thomas de Poynings, was his daughter by Margery his wife (citing Assize Roll 819, m.3, Coram Rege Rolls, Mich. 35-36 Hen. III, m.54; Trin. 37 Hen. III, m.4). (Many authors have followed the account in Blomefield's History of Norfolk [vol.2, p.178], which is essentially similar but contains a number of errors, including the identification of their mother as Agatha, daughter and coheir of Fulk de Beaufo.)
The sources cited by the Complete Peerage in the article on FitzBernard show only that (i) John FitzBernard died shortly before 30 October 1259, and left a son Ralph, aged 13, 14 or 15 and (ii) that the wardship of the land and heirs of John FitzBernard was granted on 15 February 1262/3 to Joan "de Aguylun", late the wife of Imbert Pugeis, and to their children - the wardship having previously been granted to Imbert. Possibly it was assumed on this basis that John had been Joan's first husband and Ralph her son.
Finally, Joan's share of the Aguillon inheritance seems to have passed to Robert Pugeis, her son by Imbert [see, e.g., Cal. Inq. p. m. vol.1, p.901; Rot. Hundred. vol.1, pp.461,542]. Therefore, presumably, she was not the mother of John FitzBernard, her first husband's son.