Illingworth married Mary Mackenzie Coats (b. 1883), daughter of George Coats, of Staneley,
Renfrewshire, on 16 January 1907, at
Paisley. They had three sons. • Henry George Coats Illingworth (1908–1993), married Violet Dawn Gold, daughter of
Harcourt Gilbey Gold. had issue: • Mary Dawn Mackenzie Illingworth, married
Ian Ogilvie-Grant, 13th Earl of Seafield. • James Henry Harcourt Illingworth, married his sister-in-law
Lady Pauline Anne Ogilvie-Grant. He died suddenly in January 1915 of typhoid fever. ==References==