I took a few hours tonight to check all the information I have on this Ducharme family. I believe that I said it before, but I am not an expert on these Ducharme, whose first ancestors in Québec were Fiacre Ducharme et Marie Pacreau. Mine is the Charron-dit-Ducharme family.
Nevertheless, the more I think about it, the more I doubt that Cuthbert Ducharme, born 1827 (other sources say 1832), could be the grandson of Laurent Ducharme (born 1723) and Marguerite Metivier, by a son Jean-Marie. This for the follwoing reasons:
1) 104 years is too much for a difference betweeen a grandfather and a grandson. It's not absolutely impossible, of course, but the common distance is around 60 years. 2) There is no information avilable about Laurent Ducharme and Marguerite Métivier having a son with the name Jean-Marie. 3 of their 4 sons died young, and no information at all is available on the 4th one, who likely also died young.
So I believe that there must be a mistake in the «Upper Missouri & Charles Mix County Reminiscence" by Stanley E. Votruba» mentionned in your message.
Something may lead us to a solution: there was a Jean-Marie Ducharme, born around 1796 to Paul Ducharme and an Menominee Indian. Paul himself was the son of Jean-Marie-Ducharme and Marie-Angelique Roy-Portelance. This Jean-Marie Ducharme was the son of Joseph Ducharme and Marie-Thérèse Trottier. What's more, Jean-Marie was first cousin to Laurent Ducharme.
Now both Laurent and Jean-Marie were born the same year (1723), in the same area (Montréal), and both were fur traders and voyageurs at the same time and places. Both came back in the Montréal area where they died. This may explains the confusion about Cuthbert's origin.
Does that make sense? I will be waiting to read you.