From National Archive digital images of the handwritten 1800 Census for South Carolina:
William Cox
I believe this is our William Cox in 1800. The FamilySearch.org/NARA index results show as Society Hill/Darlington, but on the actual handwritten record, it shows Greenville County. The other names on the page include: John Newlin, Henry Brasher, Thomas Brasher, John Brasher -- so it at least makes me think it's a related Cox since those are all related families.
If William is the 45+ male, which he would surely be around 70 in 1800, then the female 45+ may be his second wife, Mary Langford, the widow of Henry Langford. And the four children all under the age of 15 may be hers by her previous marriage. See below sections for all of William Cox's known children, who would all be adults and with their own households.
Free white males
Under 10: 1
10-15: 1
16-25: 0
26-44: 0
45 and over: 1
Free white females
Under 10: 1
10-15: 1
16-25: 0
26-44: 0
45 and over: 1
William Cox, Greenville Twp, Greenville County, South Carolina
From this, it's probably a young married couple
[Note: A Robert Cox is listed nearby -- who are these Coxes.??? You could make the case that this William Cox is the oldest son possibly of Robert. The ages fit and they are near each other in the Census. But are they related to "our" Coxes?]
Free white males
Under 10: 1
10-15: 0
16-25: 1
26-44: 0
45 and over: 0
Free white females
Under 10: 0
10-15: 0
16-25: 1
26-44: 0
45 and over: 0
Robert Cox, Greenville
Free white males
Under 10: 0
10-15: 1
16-25: 1
26-44: 0
45 and over: 1
Free white females
Under 10: 1
10-15: 1
16-25: 0
26-44: 0
45 and over: 0
*** Isaac Cox, Greenville County, South Carolina
[note: Nicholas Pile (Pyle) nearby]
This would mean a good estimate of Isaac's birth year is in the 1760s (the Census in South Carolina, for example, took two years, so none of this is exact). This corresponds with what we have.
The total in the household below is 13. We only know of Isaac and his wife (name unknown) and nine children. So either they had others living with them (perhaps wives of older son?) or unknown-to-us children.
The males we assume are Isaac and his sons, James, Abraham and William. We had that William was the youngest and would only be around 2 in 1800, though? So that either means we are wrong about William's birth year or that the Census marked his age wrong or that he wasn't marked at all and an older male was living in the household. We had James as born in 1778, which would make him around 22 in 1800; and Abraham born in 1783, which would make him around 17 in 1800. These two add up.
The females would be: The three Under 10 would be Sarah (born 1790) and Frances (born 1794) plus an unknown -- perhaps they counted William here? Or perhaps this is a grandchild? We assume the one 26-44 is Isaac's wife (name unknown). For the five other females then, we have four of Isaac's known daughters left: Elizabeth (born 1780), Polly (Mary), Cithia and Rebecca. This leaves one female unknown. If the oldest son, James, for example, had married, perhaps this is his wife? Or it could be a relative staying with them.
Free white males
Under 10: 0
10-15: 0
16-25: 3
26-44: 1
45 and over: 0
Free white females
Under 10: 3
10-15: 0
16-25: 5
26-44: 1
45 and over: 0
*** Abraham Cox, Greenville, Greenville County, South Carolina
[Note: Nehamiah Pain is listed nearby. Abraham married Nancy Payne (need to check if this is her father).]
Free white males
Under 10: 5
10-15: 1
16-25: 0
26-44: 1
45 and over: 0
Free white females
Under 10:1
10-15: 0
16-25: 0
26-44: 1
45 and over: 0
*** Conney Cox (widow of William Cox Jr.), Greenville, Greenville County, South Carolina
William Jr. died in 1798. He married Connie/Conney Baker. This would be her as a widow and head of household. She would later marry William Richardson.
[Note: George Croft, Frederick Croft Sen. and Jun. nearby - relatives of Rebecca Cox, William Jr.'s sister who married George Croft.
[Also note: a Joseph Newlin and Benjamin Pollard Jr. listed nearby. James Newlin and Benja. Pollard were witnesses to William Cox's 1787 sale of his Orange County, NC land.]
** Rachel Cox Long (married Thomas Long), Greenville, Greenville County, South Carolina
This census page has a lot of related families: John Brasher Sen., Samuel Braysher (Hannah Cox's husband), Laurance Brasher [all the different spellings], William Lee, Thomas Long Sen., Thomas Long Jun., William Long.
Thomas Long Sr. and Jr. seemed to take on and drop the Sr. and Jr. in different spots in records. I'm not sure which one Rachel is married to in this Census. I think she is the oldest of William Cox's children, so she very well may have been 45+ years old by 1800. I'm leaning toward the Senior in this one. That would mean her oldest son was Thomas Long Junior and had a small household on his own, as well as her other son William Long. I'm not sure how accurate this Long family tree is but it sort of lines up with the Senior's census numbers.
Thomas Long Senior
Free white males
Under 10: 2
10-15: 3
16-25: 2
26-44: 0
45 and over: 1
Free white females
Under 10: 3
10-15: 0
16-25: 1
26-44: 0
45 and over: 1
----------------------
Thomas Long Junior
Free white males
Under 10: 0
10-15: 0
16-25: 1
26-44: 0
45 and over: 0
Free white females
Under 10: 1
10-15: 0
16-25: 0
26-44: 1
45 and over: 0
*** Hannah Cox Brashier (married Samuel Brashier), Greenville, Greenville County, South Carolina
[Note - this was on same page as her sister Rachel Cox Long; This Census spelled last name as Braysher ]
Samuel Braysher
Free white males
Under 10: 2
10-15: 0
16-25: 0
26-44: 1
45 and over: 0
Free white females
Under 10: 3
10-15: 0
16-25: 2
26-44: 1
45 and over: 0
*** Sithey Cox Brashier (married James Brashier). "James Braysher"
The FamilySearch.org/NARA index lists him as Society Hill, but the actual written census records are clearly marked Greenville.
This entry and the entry for Rachel Cox Long both show these women as age 45+. That would gel with what we've always thought: that these were the two oldest, according to how the children were listed in their father's will. If they were both 45+ in 1800, then that means they were born at least around or before 1750s. This may mean then that William Cox's estimated birth years were not only 1730s, but perhaps even 1720s. Although if he died in 1814, I would think closer to 1730s.
James Braysher
Free white males
Under 10: 2
10-15: 0
16-25: 0
26-44: 0
45 and over: 1
Free white females
Under 10: 3
10-15: 2
16-25: 1
26-44: 0
45 and over: 1
*** Sarah Cox Brashier (married William Brashier) "William Bracher" and "Wm Bracher" -- There are two in Greenville County.
My guess would be that Sarah is in the Wm Bracher household. If the birth order in the will is correct, then Sarah is one of the younger siblings, possibly born late 1760s/1770+. If she has five children under the age of 10 in 1800, then she probably would have married circa late 1780s/1790. That is all very guestimating math, though. If we're wrong and the 1814 will didn't list the children in order, then it could be all up in the air.
Wm Bracher
[Note: Isaah Pain and Tho Pain listed nearby]
Free white males
Under 10: 3
10-15: 0
16-25: 0
26-44: 1
45 and over: 0
Free white females
Under 10: 2
10-15: 0
16-25: 0
26-44: 1
45 and over: 0
------------
William Bracher
[Note: James McElroy listed nearby - He was on some SC deeds for Coxes - double-check]
Free white males
Under 10: 1
10-15: 1
16-25: 1
26-44: 0
45 and over: 1
Free white females
Under 10: 0
10-15: 1
16-25: 0
26-44: 0
45 and over: 1
*** Rebecca Cox Croft (married George Croft), Greenville, South Carolina ("George Craft")
[Note: On same page as "Conney Cox" -- see above]
Free white males
Under 10: 1
10-15: 0
16-25: 0
26-44: 1
45 and over: 0
Free white females
Under 10: 3
10-15: 0
16-25: 0
26-44: 2
45 and over: 0
*** Cathrine (Katherine) Cox Lee (married Francis Lee), in Fairfield, Camden District, South Carolina -- the only sibling not in Greenville. IF this is the correct Lee, but it's the only Francis Lee that came up in SC 1800.
Free white males
Under 10: 2
10-15: 0
16-25: 0
26-44: 1
45 and over: 0
Free white females
Under 10: 1
10-15: 1
16-25: 0
26-44: 1
45 and over: 0
=========
Census categories in 1800:
Free white males
Under 10:
10-15:
16-25:
26-44:
45 and over:
Free white females
Under 10:
10-15:
16-25:
26-44:
45 and over:
All other people except Indians:
Slaves: