Stephen Simpson b. abt 1808 married Hannah Rollings at St Martin in the Fields, Westminster on 11 March 1833. They were living in Fulham in 1841 and 1851, where Stephen was employed as a gardener. In 1860 the whole family emigrated to South Australia. The 1851 census states he was born in Durham. I wonder if anyone could look for him in the PRs?
Ed