On 14 March 1826, he married the Hon. Charlotte Irby, daughter of George Irby, 3rd Baron Boston and Rachel Ives Drake. Together, they were the parents of:[1]
Hon. Henry Warrender FitzMaurice (1828–1875), who married Sarah Jane Roose, daughter of George Bradley Roose, in 1861.[1]
Hon. Frederick O'Bryen FitzMaurice (1830–1867), who married Mary Anne Taylor Abraham, daughter of Robert Taylor Spooner Abraham, in 1853.[1]
Lady Isabella Emma Elizabeth FitzMaurice (1832–1906), who married Samuel Leo Schuster, son of Leo Schuster, in 1858. After his death in 1884, she married Lt.-Gen. Hon. Hussey Fane Keane, son of Lt.-Gen. John Keane, 1st Baron Keane, in 1886.[1]
Hon. Alexander Temple FitzMaurice (1834–1894), who became a Groom of the Bedchamber to the Prince of Wales in 1867; he married Adela Mary Scrope, daughter of Simon Thomas Scrope, in 1873.[1]
Hon. James Terence FitzMaurice (1835–1917), who married Frances Rhoda Ouseley, daughter of Sir William Gore Ouseley, in 1861. After her death in 1907, he married Eleanor Palairet, daughter of Capt. Septimus Henry Palairet and sister to Henry Palaire, in 1911.[1]
Lord Orkney died on 16 May 1877.[1] He is interred in Latteragh graveyard in County Tipperary, Ireland.[6] He was succeeded in his titles by his eldest son, George.[1]