Notes for William Cody:

William may have been son of James . There are no other males besides James listed in Zedekiah's household on any tax lists. However there is another male listed in James Cody's household on the 1840 Scott County, Virginia census that fits the age of William.
William is listed as William Codey in the 1850 census, Wm. Cody in the 1860 census, William Cody and William Coda in Mahala's pension application.
The only source I can find for a middle initial is from the book, The Codys in the U. S. A., William F. Cody Line by Charles Patrick Cody (great grandson). He gives the name as William Frederick Cody. Since he also mentions William F. Cody (Buffalo Bill) and the fact that the name appears many times in the Cody line, I wonder if there is the possibility that he assumed the F stood for Frederick.
If William is the son of James, he had a brother named Frederick. The possibility of two sons named Frederick is not likely.
Descendants of Thomas Cody, (another son of James) gives Thomas' full name as William Thomas. Again it is not likely that there would be two brothers named William.
Where does William Cody fit in? For the time being I list him as a son to James based on earlier tax and census records.

William Cody enlisted in Civil War Co. C., 8th regt. Inf. at Lexington, Ky, on December 1, 1862 for 3 years or duration of war (Unionist)
Promoted to Cpl. February 1, 1863
Promoted to 2nd Sgt November 1, 1863
Promoted to lst Sgt March 1, 1864
Died of fever July 30, 1864 in General Hospital, Knoxville, Tennessee
Buried in Knoxville
"The Blue and Gray from Hawkins County (includes Hancock County) Tennessee 1861-1865" compiled by Sheila Weems Johnston. pg 185

Listed on 1850 Scott Çounty, Virginia census, age 19 in household of John B. Dorton.
Listed on 1860 Hancock County, Tennessee census age 28 living in household of mother in law next door to James Cody.

Notes for Mahala Fletcher:

1850 census Hancock County, Tennessee in household of mother Catharine Fletcher.

1860 census Hancock County, Tennessee in household of mother Catharine Fletcher but with husband William, son James age 7, daughter Catharine age 5, son John age 3, son Zedekiah age 1.

1870 census Hancock County,Tennessee head of household, widowed with son James 16, daughter Catharine age 15, son John age 13, son Zedekiah age 11, son Henry age 9, daughter Mary E. age 7 & domestic servant Frances Mabe.

1880 census Hancock County, Tennessee head of household, with son Zedekiah age 20, daughter Mary E. age 17, son Henry age 18, daughter Catharine Anderson (widowed) age 25, granddaughter Mary A. age 6, granddaughter Ellen E. age 3, granddaughter Mary J. age 2, mother Catharine Fletcher age 100, daughter in law Margaret Cody age 15 (Margaret Nichols, wife of Henry)

1900 census Hancock County, Tennessee head of household with daughter Mary E. Martin age 37, boarder Elizabeth Roberts age 21.
Mahala says she is the mother of 7 children with 5 living.

Mahala Fletcher Cody applied for a pension. She rode horseback or walked to Knoxville, where she received her first pension payment.
"The Codys in the U.S.A. , William F Cody line by C. P. Cody

According to pension papers, Mahala received back payment from the date of first application.