Romney was the son of Charles Marsham, 3rd Earl of Romney and his wife Lady Margaret Harriet Montagu-Scott, daughter of Charles Montagu-Scott, 4th Duke of Buccleuch.
His ancestors came from the parish of Marsham, Norfolk, in the 12th century.
On 30 July 1863, Romney married Lady Frances Augusta Constance Muir Rawdon-Hastings (1844–1910), a daughter of George Rawdon-Hastings, 2nd Marquess of Hastings and Barbara Yelverton, 20th Baroness Grey of Ruthyn.
[3] Together, they had five children:[4] Lord Romney died in August 1905, aged 64, and was succeeded in the earldom by his eldest son Charles.
Lady Romney died on 1 September 1910, aged 66.