What a lot of research you've done! My John is definately the retired dairyman with his wife Sarah visiting his brother-in-law, John Sanders, in the 1851 census. I agree that the widow Ann visiting William in 1851 could very well be John's mother. Based on the marriage records, she has to be Ann Phillips as she would have been too young to marry in 1793. I'm sure all the other Twoses are related somehow as this is apparently a large family in Devon and Somerset.
William the butcher was born in abt 1809 which is before James Twose and Ann Phillips were married but I suppose these things were common back then also!
I do appreciate all the time you've spent on this. Thank you very much!
Elizabeth from Canada