I put a comment on your tree.
Your great-uncle's assertions without the documentation or understanding how he evaluated the source data (or what sources he used), should be only used as a guide to your own research.
I'm guessing his work was done 20+ years ago? He didn't have the resources to do the kind of research we can do today.
My suggestion is to build out the generation of children of Narcisse Courchene and Genevieve Godin. The surnames have many variations as well as dits. You want to qualify these with more documentation before moving back.
I'm not convinced Narcisse Courchene was Jean Baptiste Durand.
In regard to the possible Metis or Aboriginal origin. If you review enough documents, that will make itself apparent.