I would like to know what source mentions him as a native of Vannes in Brittany ?
I have no doubt that he came from Brittany but I am not sure that Vannes is his place of origin.
The original family could either be DERVEN or DORVEN, both local last names.
The first names Corentin and Yvon (his son's) are also very often given in Brittany.
His wife name doesn't seem correct. ONEF is not a local name, not even a French name. May be it was HENOFF or HENAFF.