Here’s what we absolutely know about Joseph–1. He came from Canada. 2. He worked for Andre Fagot.
Based on those two things, there are some things we can feel are reasonably certain. 1. He didn’t come from Canada alone. He had some kinship ties here. 2. He had to be somewhere where he could run into Andre Fagot in order to begin working for him–either St. Louis, Ste. Genevieve, or Kaskaskia–the three towns Fagot is associated with. 3. ‘Deraque’ is an Anglicanized version of his name, because there aren’t any Deraques in Ste. Genevieve or Kaskaskia (I couldn’t find a census for St. Louis, but I’m feeling pretty confident about it.). In Ste. Genevieve, there are Durochers, who sometimes spell it DuRoche. By the 1830s, some of them are Durards and some are Deraques.
So, what we’re looking for is a family who came down from Canada and settled along the Mississippi. We might expect them to be in the fur trading business, which would explain why the Demonbreuns, through Fagot, would make business ties with them. Do the DuRochers fit the bill?
Piece of evidence one: A “Jauseph DuRoche” signs the loyalty oath in Vincennes at the same time Demonbreun does. No DuRoche is listed in the 1783 census, though, suggesting DuRoche did not live in Vincennes. (See page 57).
Piece of evidence two: Laurent DuRocher (b. 1749). He has exactly the kind of life we would expect someone in Joseph’s family to have. He came to St. Louis from Quebec as a fur trader and he married into a prominent family in Kaskaskia. His parents, Jean-Baptiste and Genevieve Durocher, also had a son named Joseph, born in 1760.
There’s one more interesting DuRocher–Auguste. (See page 155). Born in 1779, he’s a fur trader out of St. Louis who goes up the Missouri River. He does not appear to be the son of Laurent. But he does have sons named Louis and Joseph, which, as you recall, are also the names of two of our Joseph’s sons.
One might ask herself what Joseph was doing between 1760 (if that is indeed him) and 1791, when he shows up in Nashville. Thirty is awfully old for a French guy not to be married (though it appears Fagot never married. [I think it's not cool to laugh at the obvious insinuation, but no one will hold it against you if you do and just don't tell anyone.]). Maybe it’s too easy–giving Joseph Auguste, but I’m tempted.