I couldn't find a Thomas in the 1911 either ... not in Kingston. There was a 2 year old in Parry Sound though, I think?

Maybe Anthea, you can do a search in the automatted geneology site and 1911 census for a Thomas Donaldon for all of Ontario and click on any that might be the right age for Thomas in 1911, and see if any names of the people in that household ring any bells for you or your Dad

FYI: just a little note for everyone else and you, Paul, who don't know this, and for your future reference for you for any searches or anything you do, our separate Canadian areas are called PROVINCE / Provinces. (Province of BC, or Ontario, etc) We don't have "states"