I am not sure if there might be some connection here, but my grandfather was also called John Fernandes (b. 1901) with parents and grandparents who moved from Madeira to British Guiana in the 1800s. What seems interesting is that many of the first names in your ancestor's family are similar to those in my grandfather's (very large) family and I know there was a tradition of using the same names from one generation to the next. It might just be coincidence, but I am in any case interested in finding out more about the Madeiran Portuguese in Guyana and the Fernandes line. I think there is some fascinating history there.