rosie99 - I suppose it's possible. The children are all registered with Jane Campbell as mother, so that Oxnam marriage would be a bit puzzling, unless she's suddenly resorted to a maiden name?
The mention of Alexander being a 2nd son is also at the moment a mystery, as I can only find daughters born to James and Jane. As the 1st daughter is named Jane, I would have expected a son named James. The daughter born after William has the Christian name Calender, which I am assuming is either a family name or named after the place Callander.