Agnes Bainard, 2nd wife - Sources for Agnes Bainard?

That's based on an old, outdated theory having to do with the manor of Burton (Agnes) and the assumption that it "must" have come into Bruce hands through marriage.

Unfortunately it was later found that the manor and related holdings had been part of the original Bruce fief all along, and the appellation "Agnes" was added several generations later. Geoffrey Bainard may only have held it temporarily/ex officio (that is, only while he was Sheriff of York), and direct evidence for his having a daughter Agnes is lacking. (From "The Brus Family in England and Scotland, 1100-1295", by Ruth Margaret Blakely, p. 16 and note 33.) https://books.google.com/books?id=_c95jpY_joAC&pg=PA16&lpg=...

Thanks Maven, I have made changes to reflect this and noted the overview pointing to this discussion.

Then there is this from Early Yorkshire Charters: Volume 2:
See page 12
https://archive.org/details/earlyyorkshirech02farruoft/page/12

Two years late but just came across this issue in my own tree as Agnes Bainard and Robert I are 37 years apart in age