Jean C.
Although it is not really relevant to your quest on the Cain(e) and Costain connection I do share a common ancestor with Richard Costain (1839-1902).
I concur in general terms with your posting of Sunday 01st February last and confirm some statements made:-
Richard Costain (Castean), a fisherman, did marry Elizabeth (Betsy) Redhead, a farmers daughter, on the 10th January 1839 at Arbory I.O.M.
Nb. I am familar with the remarks made by Wm. Cubbon.
As my remit is the surname/family name of Redhead I will only dwell on this:-
Elizabeth otherwise known as Betsy came from a well established farming background at Ballanorris, in that area, and was the second child and eldest daughter of Robert Redhead and Jane Cubbon.
They had married on 21st April 1814 at Arbory.
Nb. This was by licence and consent as they were both young.
The Henry Redhead you found in the census was the fourth child and second son of the above Robert and Jane.
He was a Tailor and lived as a Lodger with his elder married sister Betsy Costain until he married Elizabeth or Isabella Kneen on 29th April 1852 at Kirk Rushen.
The above Robert Redhead was from a large family and one of his younger siblings James Redhead (1802-1861) was my 2xGreat Grandfather.
James was a Malster who lived in a House, still standing, at the Level Colby.
My research conducted a long time ago was partly verified by the late Messrs Noreen Cottier, (Professor) Donald Dugdale, Mrs Constance Radcliffe and Brian Lawson.
Anyone wishing to add information on the manx branch of REDHEADs can contact me initially through bt.com (Residential-York-England)
P.J.R.