Margaret Brown was born about 1749 and married Thomas Stone, signer of the Declaration of Independence, in 1762. She was the youngest daughter of Dr. Gustavus Brown of Port Tobacco, Charles County, Maryland. Margaret was described as being "adorned with elevated talents and blest with piety, and every female virtue." At the time of their wedding, they received L1000 sterling with which they purchased a plantation - the "Havre de Venture" - located about two miles from Port Tobacco.
Three children were born to Margaret/Mary Brown and Thomas Stone: Frederick (died during the yellow-fever epidemic of 1793 while studying law in Philadelphia), Mildred (born in 1771; married Travers Daniels of "Cleremont" in Stafford County, Virginia), and Margaret Eleanor (became the second wife of John Moncure Daniel of "Crows Nest" in Stafford County, Virginia).
Margaret was inoculated with small pox in 1787 but didn't receive proper treatment. Thomas watched as his beloved wife suffered miserably for weeks until she died. He was so affected by the death of his wife that his own health declined steadily. He died on October 5, 1787.
Facts are from Wives of the Signers: The women behind the Declaration of Independence, pp. 220-225.