He married Lady Mabel Florence Mary Crichton, daughter of John Henry Crichton, 4th Earl Erne of Crom Castle and Lady Florence Mary Cole, on 21 April 1906.
He fought in the First World War.2 He fought in the Captain, 1st Life Guards.
Children of Lord Hugh William Grosvenor and Lady Mabel Florence Mary Crichton:
Gerald Hugh Grosvenor, 4th Duke of Westminster b. 13 Feb 1907, d. 25 Feb 1967
Robert George Grosvenor, 5th Duke of Westminster b. 24 Apr 1910, d. 19 Feb 1979
He died on 30 October 1914 at age 30, killed in action. Having no known grave, he is commemorated on the Menin Gate Memorial, Ypres.
"England and Wales Census, 1891," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:4SWG-T3Z : 15 October 2015), Hugh W Grosvenor in household of Hugh Lupus Grosvenor, Chester, Cheshire, England; from "1891 England, Scotland and Wales census," database and images, findmypast (http://www.findmypast.com : n.d.); citing PRO RG 12, Cheshire county, subdistrict, The National Archives of the UK, Kew, Surrey.