Reading old newspapers, as one does, I stumbled upon a different obituary for the Rev John FAIRBAIRN of Greenlaw than that I had previously seen. This one was in The Free Church of Scotland Monthly (Edinburgh, Scotland), 1 Jun 1895, and contained a new interesting little snippet for my FAIRBAIRN research: "Along with his more distinguished brother Dr Patrick FAIRBAIRN, Principal of the Free Church College Glasgow, he spent his youth at Hallyburton, ... while his two cousins Dr James FAIRBAIRN of Newhaven, and Dr John PURVES of Jedburgh, had their homes at farms a few miles further west in the same district."
I've been tripping over the Newhaven James often enough in the past but had never managed to place him in any of my known FAIRBAIRN trees, his death cert showing his parents as James FAIRBAIRN and Elizabeth TAYLOR, with the only other known (to me) family being an unmarried sister Eliza.
Knowing that the Rev John's grandparents were a James and Elizabeth (PURVES) FAIRBAIRN, and quickly finding out that Dr John PURVES was the son of Peter PURVES and Margaret FAIRBAIRN, with Margaret looking highly likely to be a dtr of James and Elizabeth (PURVES) FAIRBAIRN, I've now placed the Newhaven James as brother of Margaret and the Rev John's father John (marr. to Jessie JOHNSTON).
The informant for the Newhaven James' 1874 death was his cousin, a Peter someone of Ferry Rd.
I had initially taken a stab at the squiggle being THOMSON, but have subsequently confirmed that it is actually Peter Chas PURVES, who was living in Ferry Rd in 1881, Peter Charles being the son of the Jedburgh Dr John PURVES above, and being yet another minister in the family - presumably ministering to my own FAIRBAIRNs at Morebattle, given he was the Free Church minister there in the 1861 and 1871 censuses.