Thomas Duffy died 6 Aug.1917 "Son of James and Elizabeth Duffy, of 21, Upper Gloucester St., Dublin"https://www.cwgc.org/find-records/find-war-dead/casualty-details/446467/thomas-duffy/Possibly this family? http://www.census.nationalarchives.ie/pages/1911/Dublin/Mountjoy/Hill_Street/23374/Five Joseph Duffys listed in CWGC but none of the details match your post.Where did you get information that "Thomas duffy and Joseph duffy ofthe 2nd battalion royal Dublin fusiliers are related they both died the same day in Flanders"If you search CWGC site for 'Duffy' and only put in 'Royal Dublin' as Regiment there are 22 results you can view for more details. It was on a website’ joseph Duffy 7728 died April 26 1915 no grave