After John Wayles married Martha Eppes in 1746, her father Francis Eppes IV gave the couple Betty and her mother as part of his daughter's wedding settlement. He stipulated that Betty would always belong to Martha and her heirs (rather than being part of her husband's property). Betty was trained as a domestic servant at one of Wayles' plantations.
Betty's master John Wayles was widowed three times. In 1761, after the death of his third wife, Wayles and Betty began a relationship that produced six children.
Her children by Wayles were:
- Robert Hemings (1762–1819), who purchased his freedom from Thomas Jefferson in 1794;
- James Hemings (1765–1801), freed by Jefferson in 1796 after training his brother Peter for three years to replace him as a chef;
- Thenia Hemings (1767–1795);
Critta Hemings Bowles (1769–1850), who married Zachariah Bowles, a free man of color. Sometimes called Critty, she was an enslaved domestic worker at Monticello from 1775 until 1827, when most of Jefferson's slaves were sold following his death. Critta was purchased and freed by Francis W. Eppes, whom she had cared for as a nurse when he was young, starting in 1802. (His parents were John Wayles Eppes and Mary Jefferson Eppes, Jefferson's second daughter, who had died young). She then lived with her husband at his 96 acre farm north of Charlottesville in Albemarle County.[15] She had a son, James, who was a carpenter at Monticello. After cruel treatment by a white overseer, Gabriel Lilly, he ran away about 1804.
- Peter Hemings (1770 – after 1834), served as chef to Jefferson after being trained by his brother James; and
- Sally Hemings (c. 1773 – 1835), who seems to have had a relationship with Jefferson from about 1789. She had six children, four of whom survived and whom Jefferson freed. Sally was with him to his death in 1826, after which she was "given her time" (informal freedom) by his surviving daughter Martha Randolph.
Wayles was not known to acknowledge his children by Betty, nor did he free her or them in his will. To do so would have communicated his relationship with Betty and would have required a change in Virginia manumission laws at that time. He did, though, allow certain freedoms for his children. For instance his two oldest children were taught to read and write, allowed them to earn their own money, and allowed to travel by themselves. The youngest boy, Peter, was three years old when Wayles died.
After Wayles died in 1773, all eleven members of the Hemings family and 124 other slaves were inherited by his daughter Martha Wayles and her husband Thomas Jefferson, the third president of the United States.