According to most secondary sources on the Montacute family, Simon married Aufricia "of Man".[1-6] Aufricia supposedly being the daughter of Fergus, King of Man,[1-6] and mother of at least three of Simon's children, William, Simon and John. According to another secondary source, Simon married Aufricia, daughter of Fergus and sister of Orray, King of Man. Unfortunately, an examination of primary records and reliable secondary records of Mediaeval times indicates that there is no evidence at all that Simon married Aufrica and indeed, that she was not even the daughter of Fergus.
The earliest suggestion that Simon married Aufricia was in "Visitations of the North", a now lost manuscript from the late 1400's. The manuscript claimed that Simon Montagu married "Anfrike", daughter of Fergus of Galloway. However, it then goes on to confuse Simon's son, William, who married Elizabeth de Montfort, with a younger son, Simon.
"Complete Peerage", generally a fairly reliable source does mention Aufricia in connection with Simon, but mentions that Simon's wife, Isabel, was still alive in 1290, so effectively ruling out Aufrica as the mother of Simon's known children, who were all born before that date. It then goes on to state in a footnote that "it has been surmised that Simon married Aufrica, but no evidence of such a marriage has been found." According to CP, "In 1304, Aufrica de Connoght, heiress of the Isle of Man, quitclaimed all of her rights to Simon de Montague." Since this often happens as the result of a marriage, it is evident that some have made the obvious, but unsubstantiated assumption that they did marry.
To further confuse the issue, the ancestry of Aufricia, daughter of Fergus of Galloway, as given in "Visitations of the North" and many secondary Montacute sources is correct, however this Aufrica lived some 200 years before Simon de Montacute! It is evident that these sources have confused the Aufrica who was alive in Simon's time with her ancestor, Aufricia of Galloway. Aufricia of Galloway was in fact the great-grandmother of Magnus, who was possibly the father of the Aufrica who has been connected with Simon. Another Aufricia, daughter of Aufricia of Galloway and her husband, King Olaf of Man, married John de Courcey,[12,13] and she has been suggested as the grandmother of "Simon's" Aufricia.
The last of the native Kings of Man was Magnus, who died in 1265. After his death, the title was given to the King of Scotland. In 1293, two "heiresses" made claim, Mary, daughter of Magnus' brother, Reginald, and Aufrica, on the 5th June, who'se relation to Magnus is uncertain.[12,14] Aufricia had previously appealed to the King of Scotland. On "Thursday the vigils of the Annunciation of the blessed Mary the Virgin", Aufricia ceded her all herrights as heiress to Sir Simon de Montacute.
Nothing more is heard of Mary's claim, however in 1334, Edward III, king of England, "granted the island to William de Montacute, first Earl of Salisbury, in full possession, so that he became King of Man without having to pay homage to the English Monarch. Montacute's son sold the Island in 1392, including the crown, to William le Scrope, Earl of Wiltshire. So it would seem that Aufricia's claim had enough validity that it convinced the king and that her claim was stronger than Magnus' niece, suggesting she was the daughter of Magnus, King of Man. Naturally, by the time the decision had been made, both Simon and Aufricia were dead, in fact the title and land was granted to Simon's grandson, Simon's heir having also since died.
Between 1293 and 1305 Aufricia started to use the surname "de Connoght", which is suggestive that she had married in that time to a de Connoght (Connacht or Connaught), and not to Simon.
It is clear from the above discussion that there is no substantiated evidence that Sir Simon de Montacute married Aufricia of Man, in fact such evidence as there is indicates that she likely married another. Why she assigned her claim to Man to Simon is a mystery - perhaps because he had helped her in her earlier attempts to gain her inheritance and as a Baron, he might have a better chance of succeding where she failed. It is possible that she did marry Simon and assigned the heirship to him, as was common practice, but if this was the case, her earlier husband had presumably died and the marriage to Simon would have occured after she assigned the rights to him (at the time she was still a de Connoght). If they did in fact marry, Aufricia could not have been the mother of Simon's children, all of whom were born before 1290, at which time his wife, Isobel, was still alive.