Hi Ray. Further to my message earlier today, I have now found in the 1881 census a James W Crighton born in Oathlaw in 1831, with his wife Mary (born in Aberlour 1843) and sons George W, James W, and William G, all born in Oathlaw. The census place was Oathlaw, and the head of the family is described as a farmer, with place of residence as West Mains of Finavon.
There is also another Crighton family, whose head was James, born Oathlaw 1843, wife Jane born Kirriemuir 1847, sons David and William (born Brechin), and daughters Betsy (born Brechin) and Isabella, born Fearn (I think this should be Fern, which is about 3-4 miles from Oathlaw). The head of this family was a cattleman , living at Ballownie Farm Cottage - census place Stracathro.
There are also several Crightons born in Montrose, including a David Crighton, born in 1848. The intriguing thing about him is that he had a daughter Alexa. Wonder if this could have been a cousin?
Happy hunting!