You are, I think, going to have fun with the Robertson family!!
In 1901 they are recorded as Robison, and in 1881 as Robson - indeed, sons John and Alexander both registered as Robson!
One lead is that on 1881 census (as Robson) John states he was bc.1853 Spittal, Berwickshire and Elizabeth bc.1854 Coldstream, Berwickshire.
Annette