No, I'm not related in any way to the Dunn family - just trying to help you.
Its odd but I cannot find anything at all on Joseph Edward (born 1900) after his birth - I looked for a death in Quebec, Ontario and NH but nothing and he does not seem to be in any census records or marriage record either.
So either he died young and for some reason is not in the death records, or he is there somewhere and I cannot find him.
Since your father never mentioned him I suspect he may have died young and your father was never told about him. Your Dad was born 24 years later and if Joseph Edward died as a baby or young child maybe the parents didn't speak about him.
I still cannot find the family in 1901 or 1911 census.I looked in both ON and Quebec as Edmay was born in ON but the family was shows as residing in Montreal when they crossed into US in 1920.