Hemy's father, Henri Hemy (1780-1859) was born in Germany. He volunteered for service as a military musician with the Duke of Buccleuch and came to England in 1797. He married Nancy Napier and chose Newcastle as his place of residence, evidently at 17 Eldon Place. There he taught the flute to the local gentry and many local bands. He eventually emigrated to Australia in 1852 with his brothers and sisters.
His son Henry (sometimes spelled Henri) Frederick Hemy became a celebrated musician in the North East. He had spent time at sea as a young man, and emigrated to Australia in 1850 with his family. Unable to make his way satisfactorily as a musician in Melbourne, he returned to Newcastle, where he resided on Northumberland Street for some eight years. He later lived in Gateshead and North Shields, before becoming Professor of Music at the famous Ushaw College. He had long been a Catholic convert. His many hymns include the tune 'Stella', and he may have originated the tune we know as 'Jingle Bells'. Hemy's works, including waltzes, galops, quadrilles and polkas, often with local names, fill two pages of the British Library catalogue of printed music. He also wrote a famous pianoforte tutor in 1855. He was pianist to Lord Ravensworth for may years and his orchestra played at all the fashionable venues in the region, including Alnwick Castle. Like his father, he was a member of the Theatre Royal orchestra, and possessed a fine baritone voice.
Hemy wrote entertainingly in the local press of his days in the band (particularly in the Newcastle Chronicle) on the occasion of the golden jubilee of the Theatre Royal. Hemy was also active in local politics and published a manifesto in the Shields Daily News of 3 September 1872, after failing to be elected for the Tynemouth ward. He was aggrieved at his opponents' use of professional canvassers. Hemy's proposals testify to his humanity and public spirit.
He died at his home in Hartlepool and was buried in St Andrew's cemetery in Newcastle. Eight sons survived Hemy, of whom Henri Christopher (1854-1934) of Lovaine Place, North Shields, was a musician and composer, as was Oswin Bede Hemy (1855-1916). The famous marine painter Charles Napier Hemy (1841-1917) was another. Thomas Hemy (1852-1937) , also a marine painter, was well-known for his 'Women and Children First', alluding to the heroic troops and crew aboard the Birkenhead in 1852. He also painted the Mauretania leaving the Tyne on her maiden voyage.