Just found another bit about John's offspring.
Offspring
Mytton left a number of children. Harriet Emma Charlotte was born on 23 April 1819 to his first wife. His second wife, Caroline, had a daughter and four sons: Barbara Augusta (b. 9 August 1822), John Fox Fitz-Giffard (b. 20 November 1823), Charles Orville January (9 January 1825), Euphrates Henry (b. 10 April 1826) and William Harper (b. 30 April 1827). Euphrates and Charles both died within months after their father and were also buried at Halston, as was Caroline upon her death in 1841. His two other sons and both daughters survived him. Barbara Augusta in 1847 married Colonel Poulett George Henry Somerset, son of Lord Charles Henry Somerset, a younger brother of the 6th Duke of Beaufort.
So there are descendants that will take some time to follow down.