Thomas and Boyer are fairly certainly both the children of Eleanor Bridson - in the IGI:
Samuel Radcliffe and Margaret Kelly (M. 7 Jan 1789 Malew) had many children , among whom were Jane (Ch 29 May 1791, Malew) and Elinor (Ch. 16 Dec 1792, Malew). Elinor we know.
Jane married William Quine on 21st July 1816 and one child is listed - Jane (Ch. 24 Oct 1816, Malew)
Seems to fit the jane Quine widow born abt 1793 in the earlier censuses for Castletown, not perfectly, but reasonably in the absence of better info. Again we have a couple of years difference in ages - it is difficult to decide how significant this might be for 1800-1850. I feel fairly confident about this link, but...