Alexander, Elias Patrick and Richard Cass were sons of Fields and Susanna Whitworth. The Ann who is listed with Fields is his second wife, Ann Day - there does not seem to be a record of Susanna's death, but she died between 1860 and Dec. 1863 as Fields mar. Mrs. Ann Day on Dec. 24, 1863 in Cape Girardeau Co.
In the 1880 Butler Co., MO census there is a Robert and Cordelia Whitworth -- this is really Richard. Fields and his wife and family had moved from Lincoln Co., TN sometime before 1835 to Cape Girardeau, MO.

1850 Sep 12 - District 14, Cape Girardeau Co., census (no pg# but ... pg 86 of 288 pgs):
(Fields, husband/father, is not listed with the family)
Dwlg #626/Fam #637
Whitworth, Susanna - 44 - b. TN
Alex - 21, b. TN
Sara Ann - 19, b. TN
Richard C. - 18, b. TN
Martha E. - 16, b. TN
Nancy J. (my ancestor) - 14, b. MO
Elias P. - 13, b. MO
Mary M. - 10, b. MO
Louisa - 8, b. MO
Arena - 6, b. MO
William F. - 2, b. MO
Rhoda P. - 2/12, b. MO

1860 Aug 6 - Randol Twp., Cape Girardeau Co., MO (pg 215) - lines 26-32 - Dwlg 1545/Fam 1557:
WHITWORTH, Fields - 53y/o - farmer - real est valued 1700/ persnl prop 1000 - b. Tennessee
Susan - 53 - TN
Elias P. - 23 - Farmer - personal property $75
Errina - 16 - female - (birthstate - blank)
Susan H. (looks like Susan F. to me) - 14 - (birthstate - blank)
Rhoda P. - 10 - female - (birthstate - blank)
HAMMOCK, Jos (James) H. - 22 - male - labour - TN.
(living next door is Rich C. Whitworth & wife Nancy)

1870 July 19 - St Francis Twp., Butler Co., MO; M593 Roll: 763 Page: 51 sheet 1A lines 35-39 Dwlg/Fam 8
Whitworth, Fields - 63 - farmer - TN - cannot read or write
Ann - 45 - keeping house - TN - cannot read or write
Day, Thomas - 18 - laborer - MO - attending school - cannot read or write
Millie A. - 18 - at home - MO

I do not find him listed in the 1880 census record of Butler Co., MO.