Hi Jo!
The International Genealogical Index (which can be searched at
www.familysearch.org) shows that John Cargill and Jean Roberts married at Forfar on 2nd Jan 1842.
It has records for 4 of their children (all born in Forfar)...
Elizabeth born 11th Jan 1843 & christened 25th Jan 1843
Magdalena born 21st April 1844
William born 14th Mar 1846
Alexander born 10th June 1848
There is also an entry for a John Cargil who was born on 23rd April 1810 and christened on 25th April 1810 at Forfar. He was the son of William Cargil and Magdalene Salmond who married on 18th July 1807 in Forfar.
Hope this helps!
Ju