 He was called to the bar at Middle Temple.In 1777 he married Mary O'Brien (1755-1831), who became "suo jure" 4th Countess of Orkney in 1791.Their son, born in 1778, was John Fitzmaurice, Viscount Kirkwall; he died before his mother, but Viscount Kirkwall was the father of the 5th Earl of Orkney, Thomas John Hamilton Fitzmaurice.