Dear John, I do not have any info that could help you other than this: John is the English equivalent of Yanni/Gianni, so it could definitely stand for a Greek man originally named Yanni. The other point is that Greeks who migrated, esp. to English speaking countries, more often than not adopted either the English equivalent of their first name (as described above) or Anglicised their surnames to the point where it was impossible to figure out which the source might have been -unless you knew it- or, more frequently, did both. So, yes, the names you present us with could well be hiding someone of Greek origin. I'd say, if the dates you have so far, seem to be making sense, then you might be closer than what you think. Good luck w/your search, I hope you'll be able to fill the gaps. Best, Elli