Bump of this to see if we can make any progress on this with a fresh view.
John King, baptised 1803 Kirtlington to parents Charles King and Elizabeth.
Looking for their marriage.
Charles King married 1772 in Tackley to Elizabeth Spencer. Elizabeth had a son, Charles, baptised 1770 in Tackely sworn to Charles King. They had more children together after marriage from 1773-1784. They would be too old to be John's parents, more likely Charles jnr is the father.
Can't find a second marriage for a Charles King and Elizabeth in Kirtlington or nearby places.
Two potential options from OFHS for Charles jnr:
Charles to Elizabeth RANDAL, 1799 Oxford, this ruled out because there are baptisms their of their children in early 1800s at same time as John etc being baptised in Kirtlington.
Charles to Elizabeth White, 1797 North Hinksey, supporting evidence is that they were recorded as lodgers not of the parish and there is Elizabeth White baptism 1785 in NH so they could have simply gone there to get married in her home parish. Only problem is there are a lot of Charles King's around.
At the moment John's parents are in the tree as Charles jnr and Elizabeth White... I can't think what to do to prove/disprove this.