Hi Sandra
I tried to follow that route this morning but without success.
I initially could not find his marriage to Margaret 
? who I think came from Selkirk & the 1911 census has too many Robert Hoggs even in Selkirk. I suspect they were married after the census but could not locate it.
Marriage - Robert Hogg - Maggie Patterson - 1910 - 778/ 44 - Selkirk
It might mean getting the marriage certificate to find out the parents of Robert Hogg if the poster or friend want to go down that avenue.
If they stayed in Scotland, they should appear on the 1911 census.
First child:- Maggie Hogg - 1911 - 778/ 118 - Selkirk
Second Child:- Robert Hogg - 1917 - 778/ 3 - Selkirk
Sandra
Added a possible.
This could be the 1911 census entry
Maggie Hogg - 1911 - F 22 778/ 11/ 6 - Selkirk