By 1800, his household numbered seven free white people and ten enslaved people.
In 1810, there was still seven free white people in the household but the number of enslaved people had grown to twenty nine.
The 1820 return is difficult to read but seems to be saying that there was then only one enslaved person living in the household.
There is also an Agnes Brannan living nearby in Abbeville.
The 1830 Census records Agnes Brannan, Edward Brannan, Richard and Ricd Brannan all in Abbeville.
By 1840, there are five Brannan (and variant) households:
J J Branyon
Thomas Branyon
J M Branyon
John Branyon
Thomas Branyon.
In 1850, in the US Federal Census Slave Schedule for Abbeville
Reuben Branyan with two enslaved women aged 72 and 60.
Abner Branyan with an enlsaved man aged 25 and a woman aged 20.
Thomas M Branyan with an enslaved girl, aged 10.
Margaret Branyan with an enslaved woman aged 34.
Sources
US Federal Census 1790, 1800, 1810, 1820, 1830, 1840
1850 Slave Schedule https://www.familysearch.org/ark:/61903/1:1:MVZ2-MBX (15 May 2019)
Reuben Branyan https://www.familysearch.org/ark:/61903/1:1:M8Q8-FZX (15 May 2019)
Abner Branyan 1850 https://www.familysearch.org/ark:/61903/1:1:M8Q8-FZV (15 May 2019)
Thomas M Branyan https://www.familysearch.org/ark:/61903/1:1:M8Q8-FZK (15 May 2019)