Hi Gordon
In order to save you guessing for locating them in 1841....I mean there are only 3 James Thomsons in Bothwell all the same age

.....I've looked into the crystal ball and believe you should choose the one that matches this GROS number....625/00 009/00 011.
I'm thinking that this was not a second marriage unless James managed to find two Mary Robertson's! Mary is his wife in 1841 throughout and because she is named as mother of James in 1852 and John in 1841 that puts her on either side of the gap. Perhaps they had a child or two that did not survive. We know that they went on to have James
and Andrew after Margaret!
As for Noble that lead doesn't look very promising at the moment. If he is related it will likely be distantly. If the enumerations are accurate you'll note that Noble's entire family was born in Ireland....and if his father Thomas and John's father James were brothers James would have to have been born in Ireland or Thomas would have to have returned to Ireland to marry and have his family. Certainly a very difficult if not impossible connection to unravel. You're best clue right now is James stating his birthplace as Stonehouse.....and knowing that the marriage banns were read in both Neilston and Barony. But then again you may be back as far as you can go..............
Divorce or separations were not overly common but difficult to prove. I don't think there were many formal divorce proceedings from that era....more likely that two people just stopped being a couple and went their own ways. We've seen our share of Widowed women who weren't....we've also uncovered a bigamist or two.

.....so there is really no end to the possibilities! Folks haven't changed much.............
Best wishes
Jean