I'm sorry to say that it's very unlikley that Cicely of York would have had a child named Welles as early as 1484. It's my understanding that she was unmarried at the time of the death of Richard III (August 22, 1485) and that she was married some time after that to "Lord Welles, the King's [Henry VII's] old uncle." I've read that Lord Welles was a half-brother of Margaret Beaufort by a later (or earlier?) marriage of her mother, so the King whose uncle he was would certainly have been Henry. Since Lord Welles WAS of the generation before Cicely, is it possible that he was married once before and John was the son of his first wife?