Samuel Washington (1734–1781), the eldest of GW’s three younger brothers, left Ferry Farm in the mid–1750s and settled on a 600–acre plantation in the Chotank district of Stafford County, Va., that he had inherited from his father. He also had a house in the town of Fredericksburg. Around 1770 Samuel moved his family to Harewood, an estate then in Frederick County, Va., but which was later located within the bounds of Berkeley County, Va. (now W.Va.), which was formed from part of Frederick in 1772. Samuel lived at Harewood until his death.

Samuel was a colonel in the Frederick County militia in 1771, and when his estate was within the bounds of Berkeley County, Samuel at times received rent payments on GW's behalf from many of GW's tenants in that county (see, for example, Ledger B, 31).

At his death Samuel left his family numerous debts but little money. GW and his brother Charles were among the executors of Samuel's estate, and Charles administered much of Samuel’s involved affairs. However, GW was not satisfied with his stewardship, and over the years GW was compelled to assume responsibility for the surviving children of Samuel and his fourth wife Anne Steptoe Washington. He advanced considerable sums for the education of Samuel’s two surviving sons, George Steptoe Washington (c.1773–1809) and Lawrence Augustine Washington (1775–1824), first at academies in Georgetown and Alexandria and later at the University of Pennsylvania. Samuel’s daughter Harriot (1776–1822) was also largely dependent upon GW for support. After some years of being shunted about from one relative to another, including some time at Mount Vernon, she went in 1792 to live with GW’s sister Betty Washington Lewis in Fredericksburg, but until her marriage in 1796 many of her expenses were borne by GW.