Oh, great tip - thank you! I'm now on the hunt for the oldest Fell child, William. He may be the one who married a Mary McVey in 1825 on Isle of Man, but I do not find record of his death on the IGI or in Brian Lawson's wills.
I've accounted for all of the rest of James Fell's children: Thomas, Elizabeth and Margaret all married at St. Nicholas in Liverpool and it appears that the youngest, James, died of cholera along with his parents in 1832.