I would simply add that the same James Alexander who married Mary McVey in Clackmannan in 1754 also had a fourth son named James Alexander in 1773 with his second wife (after Mary McVey) named Helen White/Whyte.
The Memorials of the Earl of Stirling (volume 1, pages 300-01) say that James Alexander senior died in 1802. There is no mention of James Alexander (1754-1802) or his sons moving to Ireland, though at least one son, John Alexander (1758-1821), almost certainly died at Loughgall, county Armagh, as a death record for that Church of Ireland parish shows. His eldest brother Alexander Alexander definitely stayed in Clackmannan, where he remained a tenant at Broadcarse. Apart from marriage records (all from Scotland), Alexander's two younger brothers Thomas (born 1768) and James (born 1773) left no known trace in Ireland, so far as I can tell.
John Alexander (1758-21), who settled at Loughgall, seems to have married a wife named Sarah and to have had up to four sons -- James, William, Henry and John -- who were all paying tithes in 1821 in Loughgall parish. My ancestor was John, who married a Sarah Berry. I'm still working on details of the other families: hope this helps.
