That's great, Donna. Thank you.
I've been looking for a surname for Mary, wife of Robert Cain b 1827. Frustratingly, all their children appear in the IGI as "Father Robert Cain, Mother Mary."
The only tiny clue I could find was an 18 year old niece in their 1881 household, called Maud Johnson, artist, born England.
I had a lucky find in my "Passenger Lists" folder where I'd stored some images of passenger lists of people arriving in the States, which at one time were available at no extra cost on a basic Ancestry subscription.
One image is from June 1936, Queen Mary sailing from Liverpool. Two of the passengers were John K Costain age 60, building contractor, born Blundell Sands, current address Caldy, Wirral, Birkenhead. Also his wife Mary C Costain age 47, born Douglas.
This slots in nicely with my theory that the Mary Cain who married John Kneen Costain (son of Richard costain 1839-1902) was very likely to have been Mary Christian Cain b 25th April 1889, daughter of Robert Edward Cain and Anna Scaddan.-------ie, the sister of Robert James Cain, father of Major Robert Cain. So this is the "cousins" connection.
Jean C