I'm trying to work out who Stephen Morrice was. I would hazard a guess that the Rev. David's wife was a Morrice and that Stephen was her brother. Mary Morrice is shown in the account (1800's) of Rev. Thomas as his niece. She helped Thomas' wife, Frances, in her teaching role.
PS Forgot just how small an area we're dealing with regarding Nantcwtta.
If we could find out when David was at Oxford then, hopefully, we could find out his father's name.