I think your John CAMMACK & Mary Polly PARKER are from a different line of CAMMACKS. I think John, b. 1789 is a son of John (b. 1753) and Margaret (PURTLE) CAMMACK. You can find information on this line in the book "James and Margaret Purtle Cammack Their Descendants and ConnectingLines" by Cecil C. Cammack, Tyler, TX, pub. 1983. I found a copy in the Indiana State Library, Indianapolis and in the Allen Co., IN Library. I am sure I have seen this information online also. I hope this is some help.