In reply to this one, Robert and Elizabeth had 11 children, not 8. They were (1) Lucy, (2) Robert, who died ? 1796, unmarried - he was a Lt. in the 15th Foot, (3) Thomas, born 17?74, d. 1834, married Mary Rush and had 1 son and 1 daughter - he was a Major in the 49th Foot; (4) Russell, (5) Frances Augusta, (6) George, (7) John Lewis, b. 1779, d. 1851, married Elizabeth Spotswood and had 2 sons and 4 daughters - he was a Lt. in the Marines, (8) William Henry, (9) my ancestor Henry Herbert, (10) a daughter, possibly called Elizabeth, who died unmarried, and (11) Maria Wilhelmine.
All this is according to the research, over many years, of my uncle Rodney Manners, now deceased, who spent his entire naval career truffling around in places like Jamaica (hence Sabrina Poole Brissett). My cousin Crispin Manners, who lives just outside Exeter, has his papers.