Archibald may have been related to Thomas, if so, it would seem that they came before 1735. The family from whom I'm related definately came from N. Ireland. There was a severe famine there in 1727-1729, so it's likely we came over around that time.
My ancestor was James Morrison (1758-1815) who married Sarah Primrose in 1786. There are several links to John's family with the Primroses, so I suspect they're related; I'm just not sure how exactly.