Thanks Evelyn,
This child died at a few days old on 11 May 1939, so any further children will be 1940 or later. Problem I have is that (I understand) when Ancestry purchased the Drouin Collection, part of the deal was they would not publish material more recent than 1940. It also seems to be very difficult to access BMD records in Canada these days. Any further children would be half-brothers/sisters of my mother-in-law. As she is now approaching 91 years old,there is some time pressure involved in resolving her questions.
Thanks again for your interest.
Simon Hayes