You should be able to trace the Manuel and Brewington families in Sampson County using normal genealogical methods since they have been there since the colonial period and owned land.
The families are interesting because they are two of the very light-skinned African American families that were culturally white--sometimes counted as white in the census and quite successful, owning many hundreds of acres of land.
The Manuel family descend from "negro" slaves freed in Elizabeth City County, Virginia in 1718 before the 1723 law which essentially eliminated that possibility for most Virginia slaves--until the law was changed in 1782.
I recently added the Brewington family to my site, but I was not able to determine their origins.
Some historians maintain that slaves did not form a distinctive African American culture until the mid-1700s. Therefore, it is not surprising that after being free landowners in Sampson County for over 200 years, the families were culturally white in the 1900s and that a three caste system of whites, former slaves, and "Indians" developed in the county in the twentieth century.