Found a number of Norman and Ronald McMullen's. Would their mother have Davison for a maiden name? Do you have a cemetery name and location for Kenneth, Norman and Ronald? Sometimes Find A Grave has the names of the parents.
Ronald Mcmullen
England and Wales Birth Registration Index, 1837-2008
birth registration: 1927 Auckland, Durham, England
mother: Davison
Ronald Million
England and Wales Birth Registration Index, 1837-2008
birth registration: 1922 Easington, Durham, England
mother: Nicholson
Ronald R F Mcmillan
England and Wales Birth Registration Index, 1837-2008
birth registration: 1929 Sunderland, Durham, England
mother: Douglas
Norman Mcmullen
England and Wales Birth Registration Index, 1837-2008
birth registration: 1932 Sunderland, Durham, England
mother: Davison
Norman Mcmullen
England and Wales Death Registration Index 1837-2007
birth: 4 November 1932
death: 1971 Durham Western, Durham, England
Norman Mcmillan
England and Wales Birth Registration Index, 1837-2008
birth registration: 1922 Gateshead, Durham, England
mother: Cockburn