John Campbell and Jean Ewing are the parents of Catherine Campbell who married James Hall in 1852.
I found it interesting that James Hall from East Lothian met and married Catherine Campbell from Argyleshire. It would seem that James must have visited Strachur in 1848 because his 2 year old son, John, can be found living with his grandparents in Strachur in the 1851 census.
Catherine must then have moved to Berwickshire where she married James in 1852.
As far as I can see, travel between Strachur and Berwickshire would have been long and difficult in the mid 1800's, I think the easiest way might have been by boat to Glasgow and then horse and cart to Berwickshire via Edinburgh.
I found the Campbell family details on scotlandspeople BMD indexes and census.