I hadn't connected your Elizabeth LAIDLAW and 2nd wife Mary BRYDON either, and have both families in my db. One day we'll make that connection we've been trying to make. I found this on Rootsweb a few years ago http://freepages.genealogy.rootsweb.com/~dagar/jardine/index3.htm#FAIRBAIRNhttp://freepages.genealogy.rootsweb.com/~dagar/jardine/index3.htm#FAIRBAIRN, which will add a few snippets to your overall knowledge of the James/Mary family.
However, I've a few puzzles with this. I have the James FAIRBAIRN who married Mary BRYDON dying in Apr 1864 at Roxburgh Mains, inf. was father-in-law James BRYDON.I only had an extract of the dth cert from a friend, but there was no mention of a previous wife in the transcript. Parents of this James were James F and Isabella CAMPBELL.
He can't be the same one that was married to Elizabeth LAIDLAW if she was described as "relict" in 1854/5 as that means widow of.