I haven't researched the Speirs back beyond James who married Agnes Hutcheson. Shoemaking seemed to be a generation to generation occupation in the Speirs family just as blacksmithing was in the Hutton family.
Yes it was George's brother James who married Agnes Hutcheson.
The CD is one of a series put out by the Troon @ Ayrshire FHS. It may be still available but I can do lookups if you wish. I'm on a trip at present so can't provide any more info until I get home later this week.