Hi Nicola, don't know if this is much help, was brought up in Hamilton and there was a family lived at the bottom of the road, their name was McKain, I was at school with the two boys of the family, one was called Frank, he would be around 52/53 by now. He lives in Glasgow now and haven't seen him for a while, unfortunately their dad whose name was Gerald was killed in an accident when they were very young, after reading your post I did a search for their dads birth records and there wasn't any, so I am assuming and I could be very wrong that their dad was your granddads adopted brother and was born with a different surname and this was changed to McKain after he was adopted, hence no records of a Gerald McKain.
