Oh my God, is this stupid story still out there? Did no one actually read the DNA report?
The Y chromosomes of the family lines of Hemings' oldest son, Thomas, and her youngest son, Eston, were tested against the Y chromosome of Jefferson's paternal uncle. Thomas was the child about whom this stupid rumor was originally started back in 1802. The test showed that he definitively was NOT related to Jefferson in any way.
Eston, the youngest son, was fathered by someone in the Jefferson family. At the time he was born, Jefferson was 64 years old, and there were 25 living Jefferson males in Virginia, 8 in the neighborhood of Monticello.
There are no contemporary writings from that time lending any credence to the idea that Jefferson was involved with Hemings, although there are several that mention the belief that his younger brother, Randolph, was.
All of this was published in the report on the genetic testing, not that apparently anyone bothered to read it.