 Through his son William Thomas Monsell, a magistrate and inspector of facturers, Monsell was grandfather to the artist Elinor Darwin (née Monsell).His brother Charles, also a clergyman, married Harriet O'Brien, who refounded the Community of St John Baptist at Clewer near Windsor after her husband's death in Italy.Through Charles and Harriet, John Monsell became influenced by the Oxford Movement and an admirer of Edward Bouverie Pusey, and also became acquainted with William Ewart Gladstone, with whom he maintained a correspondence.