There was never any question of Gundred being an illegitimate daughter of William I, but rather it was a case of a fraudulent claim that she was a legitimate daughter. The reason people used to think that Gundred was a daughter of William the Conqueror was because the monks of Lewes forged some charters which stated that. But I don't think anyone now seriously maintains that these charters are authentic.
Gundred is known to have been a sister of Gerbod, who was briefly earl of Chester under William the Conqueror. It's clear they were members of a Flemish family who were advocates of St Bertin's Abbey in St Omer, and who held Oosterzele and Scheldewindeke, although the genealogy isn't altogether clear.
Gundred was a sister of Gerbod the Fleming, earl of Chester, and possibly a
daughter of Gerbod, hereditary advocate of the abbey of St. Bertin at St.
Omer. Many sources name her as the daughter of William the Conqueror and
his wife Matilda, and she has also been put forth as a daughter or
stepdaughter of William the Conqueror. This, however, was shown to be false
many years ago. She died in childbirth.
David C. Douglas contends in "William the Conqueror: The Norman Impact Upon
England" (Berkeley: Univ of Calif Press, 1964): "The view once held that
Matilda was already married [to Gerbod] when William sought her hand, and
was then the mother of a daughter, Gundrada, later the wife of William de
Warenne, has now been conclusively disproved by the researches of Chester
Waters and Sir Charles Clay. There is no reason to suppose that Gundrada
was the daughter of either William or Matilda."
DD says: "Sister of Gerbod the Fleming,advocate of Saint-Bertin and earl of
Chester in 1070, and Frederick. Wife of William I de Warenne. She died in
childbirth on 27 May 1085 and was buried in Lewes priory (Mon. Ang. v,12).
EYC viii,pp. 6-7; A. J. Farrington, 'A note on Gherbod the Fleming, Earl of
Chester', Journal of the Chester Archaeological Society li (1984)."
Hope this helps. Polly Zashin
PLM: There is some doubt in my mind, however. Per your earlier assistance to
me; I do now have "The Chartulary of the Priory of St. Pancras of Lewes",
vol. I, ed. L. F. Salzman, and published by the Sussex Record Society in
1032. There is a lengthy charter by William Warrene nearly six pages in
length; so I will not quote it's entirety, but this bit is curious.
"..., I have given for the welfare of my soul and that of Gundrada my wife
and for the soul of my lord King William who brought me into England and by
whose license I caused the monks to come and who confirmed my former gift,
and for the welfare of my lady Queen Maud the mother of my wife and for the
welfare of my lord King William his son after whose coming to England I made
this charter and who made me Earl of Surrey,..." UNQ
PLM: It is quite clear from this charter, that Gundrada is the daughter of
Queen Maud, and the lack of a reference to William I being the father of
Gundrada is highly significant. If I were to rely solely on this evidence, I
would have to conclude that Gundrada was NOT the daughter of William I at
People have referred to forged charters from Lewes, but what is the basis of
these assertions, and which references discuss these "supposedly proven
forgeries"? The premise of such an accusation appears to be up side down, in
relation to the above charter. It seems illogical to forge a document that
makes Gundrada the daughter of the Queen, as opposed to the King of England;
which would essentially diminish her social standing, instead of elevating
it, as most forgeries tend to do?