I got stunning assistance from Susano last time I posted, so I have high hopes I may get lucky again!
My grandmother, Christina Ballantyne, had 12 siblings. I know that her elder brother, John, emigrated to Welland, Ontario, but just found her Canadian Immigration Service arrival document, on which she reported that she was to join a sister identified as Mrs. Annie Kerr (Annie Ballantyne was born ca. 1880 in Greenock, Scotland, according to the 1891 census; she was out of the home by 1901). Christina Ballantyne gave Annie's address simply as Norwich P.O. Someone hand-wrote "Sask" next to it, but I don't find any Norwich in Saskatchewan. There is a small town not too far from Welland, Ontario, called that, however.
Anyway, I haven't been able to find a marriage/child recorded in either Scotland or Canada.
I also stumbled upon a fabulous transcription of BMD records in the Greenock Telegraph which included the marriage of their sister, Margaret, to William Cunningham, plumber, in Welland on 1 July 1907; I am equally short on any other info on Margaret and William.