Lady Mary Hamilton Nisbet (1756-) was the wife of British politician William Hamilton Nisbet (1747-1822). Their daughter Mary Nisbet Ferguson (1777-1855) was married to Scottish diplomat Thomas Bruce, Earl of Elgin (1766-1841).
Martha Bruce, Countess of Elgin (1739-1810) was the wife of Charles Bruce, Earl of Elgin (1732-1771). Their son Thomas Bruce, Earl of Elgin (1766-1841), a Scottish diplomat, was married to Mary Nisbet Ferguson (1777-1855).