To put some timeframe around this whole story, I found the marriage of Charlotte Hunter & John McKenna, who were married on January 20, 1915 in Freelton, Wentworth County, Ontario. She was the daughter of Francis Hunter & Margaret Campbell. Both parties were Roman Catholic.
Now, your father's birth record is not available to the general public (if he was born ca. 1940), but if he deceased, you can obtain a copy from the Registrar's Office of Ontario. Ask for the long form certificate. It can be ordered online if you can prove he is deceased. If that is not possible, you might find a baptismal record for him in the Roman Catholic Church. You should contact the Archdiocese of Hamilton:http://www.hamiltondiocese.com/
You might also try getting a copy of Ruth's death certificate from the Registrar's Office as well, as that may provide some additional timing to the whole story.