I think I might have discovered how they were related. Via that handy letter from Alex Young:
"I was brought up to beleive that the first owners of the Brewery Barr & Heugh. In fact James Hueugh Aitken was the name he was Christened with.
James and five sisters were brought up in the Gartcows Estate, Elsie was the last sister to live in the house she moved to a cottage in Killearn to let them set on with the building of the Falkirk Royal Infirmary, Off Gartcows Road is a street named Heugh St where members of the Brewery Staff were housed.
As far as I know Elsie and the Artist sister were spinsters another was married to a Crosthwaite and another to a Banker by the name of Dewhurst, her son worked for a spell in the brewery in the Brewers Room, I dont know whether he was a qualified brewer or not.
The other sister was married to Menzies the the retail and wholesale to bookshops and book stalls.
James Aitken had only one daughter, She married Commander Robertson ( the jam people) he was on the Caledonia the training ship at Rosyth."
My guess is that the five sisters were the 5 Miss Aitkens in the subscribers list. That is, James H. Aitken's sisters.
Fascinating the the workers lived in Heugh Road (that's its real name, not Heugh Street). It's still there today and looks rather nice, with its stone semis. Take a peek:
Fascinating stuff, eh?