Betty Washington Lewis (June 20, 1733 – March 31, 1797) was the younger sister of George Washington and the only sister to live to adulthood. She was the first daughter of Augustine Washington and Mary Ball Washington. She is considered a "founding mother" of America.She was born in Westmoreland County, Virginia and married Fielding Lewis in 1750. Their children included Lawrence Lewis, who married Eleanor Parke Custis, a granddaughter of Martha Washington, and Robert Lewis.