The following people are found in early Orangeburgh County and Barnwell County, SC census records:

See Joseph Emanuel:
1790 -- household include himself, 1 male under 16 and 2 free white females.  Could be Joseph, John, unk. female & wife?

See John Manuel (ca 1790s - 1840s):
1810 -- only shows 2 boys ages 10-15 (John & William ?), 1 female over 45, and 1 slave. {He is perhaps the father of John and William}
1820
1830a1830b -- age 30-40.  John has a girl under age 5 who could be Mary B. Manuel.  John's wife was born 1791-1800.
1840a1840b -- age 40-50.  John has a girl who could be Mary B. Manuel.  John's wife was born 1791-1800.  He has four sons: births are 1831-35, 1826-30, two 1821-25.
1850  age 75.  Who was this John Manuel (born ca 1775) and his wife Polly (born ca 1790)?  He would have been 15 in 1790, so he could have been the male under 16 noted in the 1790 Joseph Emanuel record.
1850 -- age 30.   This must be John Manuel, Jr. (born around 1820).  He was living near William Manuel, age 50.

See William Manuel (ca 1800 - 1850s):
1830a1830b -- age 30-40  William's youngest girl is age 5-10, and so probably is not Mary B. Manuel.  William's wife was born 1791-1800.
1840a1840b -- age 30-40.  William has a girl who could be Mary B. Manuel.  William's wife was born 1791-1800.
1850 -- age 50.  He was living near John Manuel (Jr. ?), age 30.  William's son, William (born 1832) is still at home.
1850  -- age 25.  This must be William Manuel, Jr. (born around 1825)

Land records show "Joseph Omanuel / Manuel " or "J. Manuel" having property in Barnwell District between December 1800 and February 1807.  "John Emmanuel" is mentioned on a land plat dated January 1832.


Hypothesis:

1790 -- Joseph Emanuel is husband to an unknown wife, has a young boy (born between 1775-1790) who may have been John, and has another female of  unknown age in the household.
1800-1807 -- land records document "Joseph Omanuel / Manuel " or "J. Manuel"
1810 -- there is a "John Manuel" household, with two boys born between 1795-1800 and one female born before 1765.
1820 -- no Manuels are found in Barnwell county census records, although land records mention them between January 1800 and February 1832.
1830 -- John and William both have young girls.  Either girl could be Mary B. Manuel, but John's girl's age is more consistent with later data for Mary.  The ages of John and William's wives are within 10 years of each other.  There are no elderly women in either household.
1832 -- land records mention "John Emmanuel"
1840 -- do not alter the conclusions from 1830.
1850 -- John has died, but William is still living and has a son William (born ca 1832)  William's wife Affy was born around 1802.  A land record dated October 1853 mentions "William Mannel".
1860 -- Eva Manuel (born ca 1793) is listed living with William Manuel (born ca 1833), Lilly? Harvey (born ca 1821), {female}Gale (born ca 1836) and her grandson Virgil Manuel (born 1849).  Eva is most likely the grandmother or greatgrandmother of these people.  Mary B. Manuel (born 1829) is proved mother of Virgil Manuel (by his death certificate). Mary was most likely a daughter of  John Manuel (ca 1790s - 1840s), who had 3 daughters; the records of 1830, 1840 and 1850 show that William Manuel (ca 1805 - >1850) had only 1 daughter.  Eva appears to have been the widow of John Manuel and mother of Mary B. Manuel.
Questions:  Where was Eva Manuel in 1850?  Who is the John Manuel born ca 1775?

Possible relationships:
Joseph Emanuel (< 1770 - ?) is father to John Manuel, Sr. (1775/90 - 1850s).
The household of John Manuel is listed in the 1810 census, with his wife (over age 45) and two sons ages 10-15; however, John isn't listed.
By 1830 both John, Jr. and William have their own households.
John Sr. re-surfaces in 1850 with a wife named Polly (born around 1790) and four young people (ages 10-22) who could be grandchildren.  John Jr. apparently has died by 1850, but his brother William is still living.
By 1860, Eva Manuel (born ca 1793) is living with William, who could be her grandson.

Joseph Emmanuel, Joseph Omanuel and John Manuel are the same man within the period 1790-1850.  This man was born around 1775 and died between 1851 and 1860.  The 1810 census shows two boys who are probably John Jr. (1795/1800 - 1840s) and William (ca 1800 - 1850s).  His wife's name is unknown; she may have died before 1850, since the 1850 census shows him living with a woman named Polly who was born around 1790 and thus too young to be mother of John, Jr. or William.

John Manuel, Jr. (1795/1800 - 1840s) is likely to have been the father of Mary B. Manuel (1829 - 1875).  See 1840a1840b.  His wife may have been Eva Manuel, who is seen as head of a household in 1860.

William Manuel, Sr. (ca 1800 - 1850s)  is father to William Manuel, Jr. (born ca 1833).  William Sr.'s wife was named Affy, as seen in 1850.


Joseph (aka John Sr.) Emanuel (ca 1775 - 1850s) + ? --> John, Jr., William.  Joseph later marries Polly (born ca 1790)
John Manuel, Jr. (1795/1800 - 1840s) + Eva --> 4 sons and Mary B. Manuel (1829 - 1875)