Thank you for posting your question on History Hub!
The Federal Government does not ordinarily create or maintain birth, adoption, death, marriage, or divorce records. Such records are made and kept by State and local governments rather than the National Archives. We suggest searching substitute record sources such as probate records, church records, and newspaper records that may uncover more information about your ancestors. For more information on conducting genealogical research within our records, please visit the following link:
You can also enter your relatives' names in the search box at https://catalog.archives.gov/ but please bear in mind that the vast majority of records in our collections are not name searchable. It is also possible that you may want to use Ancestry.com (a fee based web site) to locate the records you seek or FamilySearch.org (requires a login and password but free to use) but from the sound of things you have already visited those sites. Census Records, another excellent research tool, can be accessed by visiting Ancestry or FamilySearch.
Another suggestion would be to review the FamilySearch Research wiki for South Carolina and Tennessee Vital Records to see if any additional information can be found:
Another recommendation would be to contact both the South Carolina Department of Archives and History and the Tennessee State Archives and Library to inquire if they have additional family records:
We hope this information is helpful and best of luck with your research!