Just some thoughts.
Given the lack of an obvious birth entry for James in this period under the surname of Wilson, as Annie mentions above, it could well be that your James was born illegitimate to mother Margaret Gillon.
This period as I am sure you know is a good time to search on Family Search birth indexes. James seems to show a birth year of c.1872-3?
There is one entry showing on FS for a birth at the end of 1871:
https://familysearch.org/ark:/61903/1:1:XYT1-6Z4There are a couple of other births for a James born to a Margaret Gillon, but in the 1860s.
With the reference to Row in Dunbartonshire, there is this possible census entry for 1871 (which would have been just before the birth of the James born late 1871:
Rose Gillon 75 b. Ireland
Margaret Gillon 30 b. Ireland
Mary Brown 41visitor b. Ireland
James Cassey 30 lodger b. Ireland
Richard Marshall 60 lodger b. Ireland
David Crawford 35 lodger b. Ireland
Henry Matholane 48 lodger b. Ireland
Address: 41 James St, Helensburgh, Row
Monica