 He married Harriet, the daughter of Sir David Kinloch, 5th Baronet.Sir Foster Cunliffe was uneasy about this because he seems to have concealed the origin of the fortune, omitting the word 'slavery' in a detailed history of his family's genealogy.His grandfather, Foster Cunliffe (1682–1758), made the money by becoming the main slave trader in Liverpool and mayor on three occasions.