Richard Nelson's baptism was on 5 Jan 1805 (see attached) when he was recorded as the son of Richard and Ann Pond. Given that a Richard Randall and Ann Pond married a few months later (in May) I think this must be a misprint for Richard Randall and Ann Pond. Both Richard and Ann were widowed when they married in the presence of Mary Randall (he may be the Richard marrying Elizabeth Read a few years earlier).
You have to be a little bit careful with Richard Randa/ell of Chickerell as there was another one baptised in 1804 son of Francis and Elizabeth, but this one was a little better off as his father was a yeoman with a will (1849) that mentions seven children: James, Robert, William, Thomas, Charlotte, Richard and Henry.
The most likely baptism for James is the one in 1807 in Chickerell to Thomas and Catherine Randall which fits well with:
Marriage: 1803: Chickerell: Thomas Randall and Catherine Cooper (witnessed by Rachel R)
Baptism: 1776: Fleet (next to Chickerell): Thomas Sturmey R s James and Mary Randall
Marriage: 1773: Chickerell: James Randall and Mary Sturmey (witnessed by John R and James R)
This would suggest that Richard and James are not brothers. Perhaps the connection was between Susannah (not James) and Richard, as there was a Susannah born to Richard and Ann in 1809 making her Richard Nelson's sister.
Richard
(Added later: sorry; clearly overlaps with other posts now)