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:Responding to Greg's interesting article.

The Muirs of Polkelly acquired Rowallen Estate the same way that they acquired the Caldwell Estate, when one of them, possibly Sir Robert married the Commyn heiress.The gr.gr? grand daughter Elizabeth married her cousin Robert, Earl of Strathearn who became King Robert 11 of Scotland and their son was King Robert 111.

Sir Robert's brother Sir David de More was witness to a charter of King Alexander 11. Sir David's son Sir Reginald Mure was Lord High Chamberlain of Scotland, his second son Gilchrist of Cowdams married the Heiress of Caldwell in Northern Cunningham (Ayrshire until the 19th century when boundary changes put it into Renfrewshire) his third son Reginald was one of the hostages handed over at the Treaty of Berwick in 1357 for the release of King David 11. So they were on good terms with the Bruces and probably the Stewart dynasty as well as they managed to hold on to their lands till monetry causes brought it to an end in the 20th century.

I'm afraid I can't shed any light on the exact marriage date, my copy of the Moore of Polkelly family tree is short on dates and only has "Gilchrist of Cowdams m. The Heiress of Caldwell, d.1399"
Interestingly a William Caldwell b. 1648 married Marion Mure b. 1652 both given as of Rowallen???.
The further back we go the more the Caldwell name is concentrated in Cunningham and less elsewhere. Your theory about the Plague could have some merit.
Keep up the good work. David Caldwell, Manitoba