The way I would check, is to look at the section 'citing this record' where there is a reference with numbers and letters. I have found that those who are together in the census have similar references.
There is no James Robertson there.

If you compare the births of some of the 'Robertson' children e.g Margaret and Mabel, you will see they are registered as Fyfe in civil indexes.
It all points to the couple being together before 1911 and before the subsequent Fyfe/Tofton children.