Your Isabella sounds very familiar.I am working with a family now that is descended from James and Margaret (or Mary) (McPherson) Martin who lived in the 18th century around Nairn.The ancestry continues through their son James (baptized 12 October 1777 in Aldearn, Nairn, Scotland -(IGI)), who married Janette Urquhart 30 June 1810 in Nairn, Nairn, Scotland (IGI). I don't know the ancestry of this Urquhart, but the line continues through their son William Martin, born 30 April 1815 (family dates, no evidence) who married Isabella Urquhart (1823-1880).
Isabella Urquhart was the daughter of Robert (born 1793 - family date)and Isabella (1798-1880 - family date)(Oglevie) Urquhart.Isabella Oglevie was the daughter of George and Isabella (Forsythe) Oglevie.
The Robert you mention, born 1823, may be the son of the Robert I just mentioned, and the brother of Isabella.Do you think this is the same family? Thanks so much for your replies. Bob Rafford