Thanks Jim. Maybe this child John is "Mark". I have the family on 1841 census in Sawston Cambridge. Mother Elizabeth, children Mark,Sarah, Elizabeth, James, Eliza and William. No John. The father William died in 1837 in Sawston Cambs.
The family seemed to have moved from Warwick by 1826 when their son James was born and baptised in Beddington Surrey. The family had a settlement removal order in 1832 removing them from Wallington Surrey back to Sawston Cambs.
I have found a possible marriage in Oxford for William and Elizabeth in 1820 and have e-mailed Oxford records office.
I am trying to track down where William b1791 came from. As he was returned to Sawston from Surrey with his family i thought he originated there but no joy as yet.
Cathy