Hi Tim
I just looked again at Robert Quiggin's 1851 Braddan household. Both Henry Cain 17 and Margaret Cain 20 are listed as unmarried, and there's no marriage in the IGI for a Henry Cain to a Margaret Cain in the time between the 1851 census and the marriage of Margaret to Robert Quiggin.
Do you possess the actual 1860s photos of Robert Quiggin and Mgt Cain ? If so, would you consider rescanning or photographing them to get a better resolution, and replacing the ones on your website ? It would be nice to see them with as much detail as modern techniques allow.
Jean C