Hi there,
I haven't exactly found David,but I might have the rest of his family

Are you sure about his age? If these are his parents they seem a little young!
Dad is a farmer of 120 acres.
They are living at Tollgate House,Courtland Farm,Brompton Ralph.
RG9/1605 folio 86 page 3
Anna Sellick abt 1856 Brompton Ralph, Daughter
Elizabeth Sellick abt 1818 Rose Ash, Devon, Wife
Elizabeth Sellick abt 1853 Brompton Ralph, Daughter
Florence Sellick abt 1860 Brompton Ralph, Daughter
James Sellick abt 1852 Brompton Ralph, Son
Robert Sellick abt 1812 Brompton Ralph, Head
Robert Sellick abt 1858 Brompton Ralph, Son
William Spratt abt 1840 Milverton, Somerset, Servant
William Bishop abt 1841 Bagborough, Somerset, Servant
Ann Hooper abt 1845 Brompton Ralph, Servant
I also found a Samuel Sellick born 1843 in Brompton Ralph, living with the Bodley family in Marylebone London,working as an apprentice to a Grocer.
But where is David

Hope this helps,
Regards
Carol