 Dacre was the son of Sir Thomas Fiennes and Jane Sutton daughter of Edward Sutton, 2nd Baron Dudley.When his father died in 1528 he became heir apparent to his grandfather's title and the family seat at Herstmonceux Castle in Sussex, and he succeeded to the title at the age of approximately 19 in 1533.In 1536 he married Mary Neville, daughter of George Neville, 5th Baron Bergavenny.