This is what I have found and the DENYER SMITH marriage doesn' t tally with the census.
Nathan was in the 3rd. Bn. King's Royal Rifle Corps abd died 21 August 1918
There is a marriage of Alfred Jupp DENYER to Mary Jane SMITH in 1887, but according to the 1911 census they had been married twenty years and only had two children born alive.
This is looks like the corrrect marriage for Nathan's parents.
Alfred DENYER (no middle name) to:-Mary Jane WALDER June quater 1895 vol 2B page 399, this looks more like the marriage of your great grandparents. This also fits with Victoria's name.