Justin Huntly McCarthy was the son of Justin McCarthy, MP, novelist and historian. His first marriage was to Marie Cecilia Loftus (1876-1943), a mimic whose stage name was Cissie Loftus. They divorced in 1899, and he married for a second time to Louise Killick in 1908.
Justin Huntly McCarthy was a dramatist, novelist and historian. Whistler corresponded with him about journalistic matters. He lived successively at 48 Gower Street; 48 Bedford Square; 20 Cheyne Gardens; and 31 King's Road, Brighton in 1898.
Who's Who, London, 1905; 'Mr. Justin Huntly McCarthy Dramatist, Novelist, And Historian', Times, 23 March 1936, p. 18.