Looking for info: Joseph, Robert, Sarah DeMarcus - TN 1873

Hi,

recently found out my great grandfather Joseph Ralph DeMarcus was born in Tennessee around 1873, to parents Robert and Sarah DeMarcus (nee Justice). We found the 1880 Knox County census document noting their family, which also included my great grandfather's siblings, John, James, and Flora. Robert is listed as being black, while the rest of the family is listed as mulatto.

Any information about the family would be appreciated. We would love to know more about Robert and Sarah's history, or anything else about their family.

Thank you!