May 11, 1889 - January 12, 1921
Elwes was married in Kensington on 11 May 1889 to Lady Winefride Mary Elizabeth Feilding (died 24 February 1959), National President of the Catholic Women's League, daughter of Rudolph William Basil Feilding, 8th Earl of Denbigh and Mary Berkeley. They lived at The Manor House, Brigg, Lincolnshire, and at Billing Hall, Northamptonshire, and had six sons and two daughters together:
Robert Geoffrey Gervase John Elwes (1890–1956), First World War soldier
Rudolph Philip Cary Elwes (1892–1962), Coldstream Guards Captain
Francis Guy Robert Elwes (1896–1966), architect and interior designer
Monsignor Aubrey Valentine Denis Elwes (1899–1966 Brigg, Lincolnshire), Roman Catholic cleric
Sir Richard Everard Augustine Elwes (1901–1968), High Court judge and Recorder of Northampton
Simon Edmund Vincent Paul Elwes (1902–1975), a portrait artist and Royal Academician; grandfather of the actor Cary Elwes.
Margaret Elwes, who married Lt. Col. J. E. Sandars of Gate Burton Hall. They had one daughter, child actress Clare Sandars, who married Sir James McEwen, Bt.
Clare Mary Alice Cynthia Catherine Celia Elwes (1905–1998), who married 1940 Westminster Cathedral Sir John Henry Keswick, KCMG (1906–1982), and had one daughter Margaret, known as Maggie Keswick, gardening author (1941–1995), who founded Maggie's Centres for those suffering from cancer.[40] She left two children by her husband, the landscape architect Charles Jencks.