Hi Kevin,
here are some possible leads to follow up. Any other suggestions are very welcome.
1. If I could find out what happened to Beatrice, William, Helen, Colin and George Mackison from Dunblane I might find something linking them with Ann, Catherine, James & John (if there is a connection to be found).
2. James Mackison senior was a Distillery Worker (according to the death certificate of his daughter Catherine Mackison). There hasn’t been a distillery in Dunblane, as far as I can find out. Did he move away from Dunblane to work in a distillery in later life? Were Ann, Catherine and John younger siblings born outside Dunblane?
3. James Mackison baptised in 1789: could he be anyone other than the James Mackison who married in Bannockburn in 1812? I haven’t found anyone else who fits the bill but this isn’t conclusive and I should review the information available as I first tried this process of elimination in pre Internet days.
4. I might look again at Hugh Forsyth’s will & testament. If he left money to Robert Mackison, Ann Mackison and Mrs John Eadie he may have left money to other relatives of his wife Catherine Mackison.
5. George Mackison bapt.1794 in Dunblane adopted the Maxwell alias (common to a lot of Mackisons) so he was George Maxwell when he married Mary Jack in 1814. He was a ploughman and lived in Muthill, I think. Some of his descendants settled in New Zealand. He might be worth investigating with the hope of finding a connection.
6. The fact that the baptismal records of the children of James Mackison (Ann Mackison’s brother) haven’t been found in Bannockburn suggests James might have been a member of a seceding church. Likewise, his parents might have been members of the same church, which would explain why the baptismal records of Ann, James, Catherine and John haven’t been found in the Church of Scotland records.
7. A look at the Kirk Session records might throw something up but since they are not indexed this could be a forlorn task. A very long shot.
Presently I am inclined to think that James Mackison, who married Margaret Sharp in 1781, was probably born in Bannockburn. He was married there and since there had been several generations of Mackisons living there the most likely scenario is that he was born there. However, since there is no known record of his baptism in Bannockburn/St. Ninian’s then other possibilities remain valid.
At the moment I am working on my English family history, with lots of easier lines of enquiry. Feel free to follow up any of the above leads.
best of luck, Jim