Following the death of Lord Fairfax in 1781, Martin took his uncle's housekeeper Mrs. Crawford as his mistress, and fathered a daughter by her. Mrs. Crawford remained Martin's mistress for several years until her death. Their daughter married British captain Francis Geldart; however, she died without issue soon after their marriage, and Martin gave Geldart of Greenway Court and a number of slaves. Following the death of his daughter, Martin employed housekeeper Betsy Powers at Greenway Court. Martin died unmarried in 1798, and his will dated July 24, 1794, was proved on October 1, 1798. In it, he bequeathed his Greenway Court estate and an adjoining to his housekeeper Betsy Powers. Powers also inherited "all houses thereon, household goods (except plate and watch), one half of stock of horses, cattle, sheep and hogs and choice of ten slaves". Martin's living sisters Frances, Sybilla, and Anna Susanna Martin received "all moneys, and remainder of personal property" not bequeathed to Powers. Each of the executors of Martin's will received ten guineas. Martin bequeathed the remainder of his property and the of Greenway Court, should Powers have predeceased him, to his will executors Gabriel Jones, Robert Mackey, and John Sherman Woodcock to divide into parcels and sell, the profits from which were to be given to Martin's sisters. Powers also received a chariot, harness, and in Stafford County near Falmouth. Following Martin's death, Powers married W. Carnagy.