The information below is taken from: A Genealogical and Heraldic History of the Extinct and Dormant Baronetcies of England, Ireland and Scotland by John Burke and John Bernard Burke, 2nd edition. Sir Robert Cotton (1669-1749) appears on page 138, although the section on the family (Cotton, of Connington) begins on page 136. The title was created in 1611 and went extinct in 1752. This family is one of three Cotton families to receive a Baronetcy in England; the others are the Cottons of Landwade and the Cottons of Combermere.
"v. Sir Robert Cotton, of Gedding, in the county of Huntingdon, who m. first Elizabeth, daughter of ____ Wigston, esq; and secondly, Mrs. Morton. He died 12th July, 1749, aged eighty, and was succeeded by his son,
vi. Sir John Cotton [this is the John Cotton who was identified as Mrs. Whitfield's first cousin] who m. Jane, daughter of Robert Burdett, bart. of Bramcote, and had one son and four daughters, viz.
John, died at Durham of the small-pox, 15th November 1739.
Jane, m. in October 1741, to Thomas Hart, edq. of Warfield, Berks.
Sir John d. 27th March, 1752, when the BARONETCY became EXTINCT."
So if Mrs. Whitfield, is Sir Robert's niece, it follows she is descended from either one of Sir Robert's siblings or possibly a sibling of one of his two wives. Sir Robert Cotton's father was Sir John Cotton (1621- 1702) and Sir John had children by two successive wives. The people highlighted in yellow are Sir John Cotton's children and Sir Robert Cotton's siblings, and the people highlighted in pink are Sir Robert's nieces and nephews. The third generation is highlighted in green. Sir Robert himself is highlighted in blue.
"He m. first, Dorothy, daughter and sole heir of Edmund Anderson, of Stratton and Eyworth, in the county of Bedford, who had issue,
John, who m. Frances, daughter of Sir George Downing, bart. of East Hatley, in the county of Cambridge, and dying in the lifetime of his father, anno 1681, left two sons and a daughter, viz.
John, successor to his grandfather.
Thomas, m. Frances, only daughter and heir of William Langton, esq. of Peterborough, and left an only daughter, Mary.
Frances, b. 1677, m. to William Hanbury, esq. of Little Marcle, in Herefordshire, and had issue*
(footnote: The daughters of Frances Cotton and William Hanbury were,
Mary Hanbury, m. to the Rev. Martin Annesley, D.D., vicar of Bucklebury, Berks, and had issue....
Elizabeth Hanbury, m. to Thomas Neale, esq.
Frances Hanbury, m. to F. Bareel, esq.
Catherine Hanbury, m. to Velters Cornewall, esq. of Moccas Court.)
Dorothy, m. to ____ Dennis, esq., of Gloucestershire.
He m. secondly, Elizabeth, daughter of Sir Thomas Honywood, knt. of Marks Hall, Essex, and sister and heir of John Le Mott Honywood, esq....By this lady he had several children, but only three to survive, viz.
Robert, who succeeded as fifth baronet [i.e. Mrs. Whitfield's uncle].
Elizabeth, m. first, to Lyonel Walden, esq. of Huntingdon, and secondly to ___ Smith, esq. of Westminster; by her first husband she had,
Lionel Walden, who d. unmarried.
Elizabeth Walden, co-heir to her brother, m. first, to Charles Pitfield, esq., and secondly, to Talbot Touchet, esq. By the former she had,
Charles Pitfield, who m. Miss Ashley, daughter of Solomon Ashley, esq., M.P....
Elizabeth Pitfield, m. to Edward Bigland, esq. of Long Whatton, in Leicestershire.
Hester Walden, co-heir to her brother, m. Humphrey Orme, esq. of Peterborough, captain in the royal navy, and had a son,
Mary Honywood, m. Doctor Roger Kenyon, and died s.p."
The following excerpt, which goes over much of the same information, is from a contemporary book, The English Baronetage, Vol. 1, by Arthur Collins, printed in London in 1741. It has a fabulous title page which I can't resist showing:
You'll notice the name Whitfield doesn't appear anywhere in either family record. How annoying.
I think it's time to consider the other possibility, that Mrs. Whitfield is actually a relative of one of Sir Robert Cotton's wives and is only connected to Sir Robert by marriage. His first wife was Elizabeth Wigston, and his second was "Mrs. Morton" (really? no first name? no parentage? are they trying to make it challenging?). Now to track down these two ladies' siblings and their children....