The 1950's is a tough decade to research family. The 1940's almost as bad. In the USA, you can find information from the 1930 census, but I don't know about Canada. I'm guessing 1921 is the latest there.
What I can mention is that there "many" KERR families arriving in Canada during the 1800's, so there were hundreds of KERR's in Canada after 1900. And probably many more KERR's arriving in early 1900's. And they would have spread out across all the Provinces.
My KERR ancestors arrived in Canada in 1820's and settled in the Province of Quebec. There were 5 couples, either KERR or HENDERSON, and they all had many children.
Have you posted your query on the Message Boards and Mailing Lists for the Province of Ontario? And have you searched the archives of the Ontario Lists and Boards for mention of your John Keith KERR?
You didn't give a guess as to when he was born, but, if it was between 1900 and 1920's, you might be able to find his parents in the 1911 Canadian census.
You could also put his name into a search at www.familysearch.org
and see if anything comes up.
Betty (near Lowell, MA, USA)
(on Lists for 10 yrs.; now an Admin for 9 Lists,
including CAN-USA-Migration and LAURENTIDES (for the Laurentian Mountains in Canada) )