It's generally accepted that Jefferson fathered a child by raping Sally Hemmings, though I've read historians as recently as the Nineties dismiss the idea with scorn. Monticello has about her:

Sally Hemings had at least six children, who are now believed to have been fathered by Thomas Jefferson many years after the death of his wife. According to Jefferson's records, four survived to adulthood. Beverly (b. 1798), a carpenter and fiddler, was allowed to leave the plantation in late 1821 or early 1822 and, according to his brother, passed into white society in Washington, D.C. Harriet (b. 1801), a spinner in Jefferson's textile shop, also left Monticello in 1821 or 1822, and passed for white. Madison Hemings (1805-1878), a carpenter and joiner, was given his freedom in Jefferson's will; he resettled in southern Ohio in 1836, where he worked at his trade and had a farm. Eston Hemings (1808-ca. 1856), also a carpenter, moved to Chillicothe, Ohio, in the 1830s. There he was a well-known professional musician before moving about 1852 to Wisconsin, where he changed his surname to Jefferson along with his racial identity. Both Madison and Eston Hemings made known their belief that they were sons of Thomas Jefferson.

/u/georgy_k_zhukov wrote about the wider social attitudes and commonality of the sexual abuse of enslaved people in our recent Slavery AMA