Mackworth was the son of
Sir Humphrey Mackworth of Gnoll, Glamorganshire, MP for
Cardiganshire, and his wife Mary Evans, daughter of Sir Herbert Evans of Gnoll. His brother was
William Mackworth Praed. He was educated at
Westminster School and matriculated at
Magdalen College, Oxford, in 1704. He was admitted at
Inner Temple in 1708. On his father's death in 1727 he inherited the Gnoll estate and substantial coal mining and copper smelting interests in the Neath valley. He married Juliana Digby, the daughter of
William Digby, 5th Baron Digby on 24 April 1730. ==Career==