Have you ever thought to get a birth certificate? That might indicate the name of your father. Where did the Keast name come from? Your adoptive parents? If so, it wouldn't be any help.
There are Keasts in almost all provinces in Canada. You might want to try www.whitepages.ca and type in Keast for all of Canada. I have all the names, addresses and phone numbers for Keasts from coast to coast from that source.
My Keast line comes from Cornwall to Ontario, then west to Alberta.
Les (Dr. Leslie Robert Keylock, oldest son of Daisy Louise Keast Keylock)