Hi Mistey
I assume that you found Thomas Harris details from the IGI. Are you aware that he has several siblings also listed?
If you do a search on the IGI using the Batch Number P008921 (batch number for Moreton Corbet found on the Hugh Wallis site
CLICK HERE) you will find the following:
William Christening: 16 AUG 1792 Moreton Corbet
James Christening: 03 JUN 1795
Mary Christening: 24 SEP 1796
Ann Christening: 31 MAY 1789
Henry Christening: 04 JAN 1788
Joseph Christening: 23 MAR 1794
John Christening: 05 JUN 1786
All with parents John and Abigail Harris.
Not an answer to your question about John (snr) parents but still helpful I hope.
Jan