Thanks a million, Tony!This is definitely the right person: he has the right birth date and birth place, place and date of marriage, and wife's name.Also, the number of their children and his father's first name.
It never occurred to me that my great-grandparents might have officially preceded my grandfather's name with the name Joseph, according to tradition.(On my mother's side of the family she and all of her sisters had the first name Marie, according to that tradition.)
By the way, I am the second, but sole surviving, son of Joseph Georges Henri's oldest son.
I'll be looking again at the genealogies posted online.It's nice to know that we're "real" Fontaines.