My family conveniently named every first son -or son who was to inherit their coachworks "John Alexander Rounsiful Sellers, down the generations right to my grandad, who broke the tradition and called his son "Frederick John Eric" and I have more information than any genealogy site can provide from that date.as my parents did extensive research on my Father's family and their Exeter coachworks. John Seller began this in 1929. I know he married Rebeckah Davills and was a head coachman before he started the coach works. The family lived in North Street at the time and the marriage record says this John "John Seller of Broadclyst."
However, is there a way to go further back? I have several possibilities. Whoever his parents were, they will have married under St Thomas the Apostle. I would think, in Crediton or Broadclyst, but I have run out of ideas. Several different parentages might fit. And of course, his father may not have been born in Devon at all.
(This John had a son he called "John Davills Sellers" who married Ann Rounsiful or Rounceville or any other spelling that sounds like it which is where the family name came in.)