Thanks for the photo of the gravestone which includes my 2nd great grandfather James Alexander's brother Alex! Have you had a chance to see if James Alexander's gravestone is at the Old Logie Churchyard?
I know what you mean about the Esq. I believe the Thomas Carnegie Esq of Craigo, who fathered a Mary Carnegie, was the 4th Esq of Craigo, so from a wealthy line of lairds. Unlikely that this Mary's father would be the son of a Cotter Man (Thomas, son of Alexander Carnegy). Just that the dates line up so nicely with Mary born the same year as John Alexander, and married in Marykirk. There were certainly lots of Carnegies in the area at that time.
Do you have the death certificates for John and Mary? Please pass them on to me if you don't mind as I haven't found them yet.
Cheers,
Brian