Jefferson–Hemings controversy
The Jefferson–Hemings controversy is a historical debate over whether there was a sexual relationship between the widowed Thomas Jefferson and his much younger slave and sister-in-law, Sally Hemings, and whether he fathered some or all of her six recorded children. For more than 150 years, most historians denied rumors that he had sex with a slave.
Source: Wikipedia — Jefferson–Hemings controversy (CC BY-SA 4.0)