Completely circumstantial of course but on his service record is a letter addressed to the C.O. Rifle Brigade from his sister where she states she is his sole surviving relative & is asking for his death plaque.
She's refused on the grounds that it went to his widow (Edith). this is dated Nov. 1920 when Edith had remarried (assuming). Stating she's his sole survivor eludes to her believing Edith isn't entitled which indicates a remarriage by the time of the letter.
Doesn't answer the question but does look promising.
Edith (Trafford) & Mullock married 23/10/1917.