Jonathan was born in Staffordshire on 30 October 1717, the eldest of the four children of steam pioneer Joseph and Rebecca (née Haywood) Hornblower.
A notable figure, Jonathan was born in Staffordshire on 30 October 1717, as the eldest child of a pioneering family, with his father Joseph being a trailblazer in steam technology and his mother Rebecca hailing from the Haywood family.