There is some doubt as to who the father of Joan Bigod (aka Joan Bygot) was. See discussion in Browning, Charles. Americans of royal descent, 7th ed. Baltimore : Genealogical Pub. Co., 1969, Corrigenda, pg. A. The ancestry back from Joan is classed as uncertain, but seems to be royal in any event. The ancestry given in the Mrs. Philip H. Cooper genealogy, Browning, pg. 306, shows Joan as a daughter of one Roger Bigod. Joan's Bigod line is altered somewhat, showing her a a daughter of John, a son of Roger (see below).
The Internet sites I have searched vary in their information on the Bigods. Each shows information not included in the others. The Bingham Genealogy Project did have a reference to a Joan, but she showed as a daughter of Hugh, the Justiciar of England.
The claim of Joan as a daughter of Roger is supported by the WWW site:
(http://www.tiac.net/users/pmcbride/james/f024.htm) - Paul B. McBride's Genealogy Page, which states:
John Bigod, Knight, heir-in-law, brother to Roger, whose right seems
to have been annihilated in this very unjust and extraordinary manner, and so completely destroyed that he did not even inherit any of the great estates of his ancestors. He left a son, Roger Bigod, Knight, of
Lethingham. He left a son, John Bigod, Knight, who had a daughter, Lady
Joan Bigod, who married William Chauncy, Knight, last Baron of
Skirpenbeck, in Yorkshire. This line descends in seven generations to
Rev. Charles Chauncy, Doctor of Divinity. He removed to New England
in 1638, and became the second President of Harvard College,
Cambridge, MA. Rev. Charles Chauncy of the mid-1700s was a close
associate and personal friend of Jonathan Mayhew. Together they are
credited with contributions toward the American Revolution. See his
lineage in the Mayhew Line of Volume III.
This is the lineage I have included.