More possibilities if your James was killed in action ...
Commonwealth War Graves Commission Register
Name - MILLAR , J
Rank - Private
Service No. 21/152
Death Date - 01/07/1916
Age Unknown
Regiment - Northumberland Fusiliers
Nationality - United Kingdom
Grave/Memorial Ref. - VII. A. 7.
OVILLERS MILITARY CEMETERY
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Possible:
GEORGE LIDDELL MILLER married MARJORY REID FOREST
on 10 MAY 1870 Duddingston, Midlothian, Scotland
OPR
1881 British Census
George L. MILLER Head M Male 38 Scotland Bookseller
Margery MILLER Wife M Female 38 Scotland
William MILLER Son Male 9 Alnwick, Northumberland, England Scholar
Thomas MILLER Son Male 8 Alnwick, Northumberland, England Scholar
Jessie MILLER Daur Female 5 Alnwick, Northumberland, England Scholar
James MILLER Son Male 1 Alnmouth, Northumberland, England
Dwelling 35 Marygate
Place Berwick Upon Tweed, Northumberland, England