It's what I though initially Abydos but, I now tbelieve that you have one correct family.
Tracking them on census data after their marriage is fairly easy as they never left the Maryhill area.
The only difference is the name isn't Ferguson, it's Grant.
This is totally unconnected but some time ago, i did some research on a complicated family called McIntyre who lived in Keppochhill Street.
They too came from Kilchoman( Islay) in the same time period.
I noticed at the time that this area seemed have a high concentration of Islanders
