I still have trouble with Caldwell's descended from the Chancellor when his property passed through an heiress. Normally this means he had no male heirs. Often it was part of the condition of Scots wills that the husband of the heiress had to adopt the wife's family name in order to inherit the estate but there is no mention of this in respect of the Mure inheritance of th Caldwell Estates. Consequently there were no male Caldwell's descended from the Chancellor.
All references that I have read say "It is said that Godfrey Mure inherited the estates by marriage to an heiress" The source was obviously not precisely sure of that fact.
I agree that there were other lines descended from Caldwell's running in parallel to the Chancellor - many in fact. But the poor old Chancellor didn't have any sons as far as I can see.
I confess that I have not read Mr RM Sibert and I ask if anyone who has might show us how he traced the family tree of Wiliam Chancellor of Scotland 1350-52 to William of Straiton circa early 1600's? thats 250 years or approximately 10 generations - I am struggling to do that (with my much less famous ancestors) even with the help of the internet, modern publishing and the friendly help from your site.
With respect I think that the erudite Mr Sibert might just have found two famous Caldwell's at different points in history and drawn a dotted line between them.

I can give you two more tittilating bits of information - but it about all I have:
"The first mention of (Caldwell) appears in the Maitland Club papers (1882) ... there is an entry 'Monestum de Passelat 1292 Caldwell'" reference the Late Mrs Lesley Gordon.
"William Caldwell of that Ilk - prebend of Glasgow 1342 Entry of fee (Excheq Rolls) Chancellor of Scotland 1350-52. Most of the Estate went to the female line 'Easter caldwell' the tower."
"Patrick? Kinsman of William probably bbrother from whom descended he Caldwells of that Ilk. 'Gudemen of Caldwell'. He only inherited besides the title a small part of the estate 'Nedder or Little Caldwell' or 'Hall of Little Caldwell'"