He is s of Anthony William GARTHWAITE 1917-72 (s of Sir William GARTHWAITE 1st Bt 1874-1956) and Hon Waveney Mancroft SAMUEL 1916-86 d of 1st Baron MANCROFT 1872-1942. He m 1982 Caroline C b 1946 reg Q3 Devon d of Thomas William WILLBOURNE by his 1944 m (reg Q4 London) to Nellie ADAMS 1911-88, and had three sons (the first Julian m 2020 with at least one dau, the 2nd Felis is unm in DPB and the 3rd is civil partnered but showing no issue).
Julian’s dau’s birth: https://groups.google.com/g/peerage-news/c/Y-ZA8WW9puM/m/jle7xBuPAwAJ