Son of Thomas and Elizabeth Ann (nee LEESON) MOFFET of Watford.
His parents married 1887 in the Watford district. Elizabeth died 3 February 1927 in Watford aged 68, and was buried 7 February in Vicarage Road Cemetery, Watford. Thomas remarried 1928 in the Watford district to Lilian Maud CANACOTT; he died 3 March 1938 in Watford aged 77, and was buried 7 March, also in Vicarage Road Cemetery. Lilian died 12 September 1951 in Watford aged 64.
John was born 17 May 1888 in Watford, and attended Watford Grammar School from September 1896 to July 1903. He was further educated at the City & Guilds of London Technical College, Finsbury, London, and Manchester University where he gained a B.Sc (Hons), A.M.I.E.E.
He has an entry in the National Probate Calendar.
On the 1891 Census, aged 2 he lived in Watford, with his parents and no siblings. On the 1901 Census, aged 12 he still lived in Watford, with his parents and one sibling. On the 1911 Census, an electrical draughtsman aged 22, he was a boarder in Horwich, Lancs.