John Bacchus Dykes was born in Hull, England, the fifth child and third son of William Hey Dykes, a ship builder, later banker, and Elizabeth, daughter of Bacchus Huntington, a surgeon of Sculcoates, Yorkshire, and granddaughter of the Rev. William Huntington, Vicar of Kirk Ella. His paternal grandparents were the Rev. Thomas Dykes, LL.B., and Mary, daughter of William Hey. He was also a cousin of the Rev. George Huntington. Dykes was a younger brother of the poet and hymnwriter Eliza Alderson, and wrote tunes for at least four of her hymns.