Hi Val
I don't know whether you have only searched the free websites but if so - these are by no means complete - particularly for the years you need
Do you have any firm evidence that they lived into adulthood?
If they married, it would probably have been in the 1930's so the only way is to trawl through all the marriages on the GRO index from 1930 onwards.
If they died in infancy - you would need to trawl the GRO death index from 1912/1914 onwards.
If you live in the UK, you can search the full GRO indexes for free at your local main reference library. A copy of the GRO index is also available at each LDS family history centre within the UK and all other countries.
The full GRO index is also online and can be searched for a small fee at
www.1837online.com