In a quick Google search, I pull up a 1999 article in the Cincinnati Enquirer quoting a descendant of Madison Hemings named Priscilla Lanier saying she only learned of a link to Jefferson in the 1980s, when a cousin began doing genealogical research. So at least in this case, the history of a link to Jefferson was not passed down through the generations. There wasn't an oral tradition of a link to Jefferson.

I appreciate the information in this article, except for the last sentence, which is not correct. The sentence reads: "DNA testing in the late twentieth century, however, found no genetic link between Hemings and Carr descendants, refuting the assertion that Samuel Carr or his brother Peter had fathered Sally Hemings’s children." The DNA testing led by Dr. Eugene Foster in 1998 only involved a test on one descendant of one child of Sally Hemings -- John Weeks Jefferson, a descendant of Eston Hemings. Further, the oral tradition in the Eston Hemings family had always been that they were in some way related to Thomas Jefferson, most said through an "uncle." No DNA tests have been done on the descendants of the other three children of Sally Hemings who lived to adulthood. Two of those children "passed" into white society and are lost to history. The descendants of Madison Hemings, the fourth child, have not been tested. In sum, there has been no refutation of the assertion that Peter or Samuel Carr were involved in a long-term relationship with Sally Hemings and fathered children by her. Both Peter and Samuel Carr were in their 20s and 30s when Sally Hemings was getting pregnant and bearing children, while Thomas Jefferson was in his 50s and 60s.