One of his granddaughters, the daughter of his son Alfred Roosevelt, Elfrida Roosevelt, married Sir Orme Bigland Clarke, 4th Baronet.
Their second son, Frederick Clarke, was father of the 4th Baronet: Sir Orme Bigland Clarke, 4th Bt.
Sir | Sir Walter Scott | Arthur C. Clarke | baronet | Baronet | Sir Arthur Conan Doyle | 4th United States Congress | Sir Robert Peel | 4th | Sir Arthur Harris, 1st Baronet | Cam Clarke | Sir Raylton Dixon | Sir Harold Hillier Gardens | Sir Fitzroy Maclean, 1st Baronet | Ron Clarke | John Montagu, 4th Earl of Sandwich | California's 4th State Assembly district | Sir Francis Baring, 1st Baronet | Warren Clarke | Thomas Howard, 4th Duke of Norfolk | Sir William Temple, 1st Baronet | Kenneth Clarke | Clarke Carlisle | Charles Lennox, 4th Duke of Richmond | Benedict Calvert, 4th Baron Baltimore | Windham Wyndham-Quin, 4th Earl of Dunraven and Mount-Earl | Sir Richard Fanshawe, 1st Baronet | Shirley Clarke | Ronald J. Clarke | Richard A. Clarke |
His father, William Harcourt Isham Mackworth (1806—1872), a younger son of Sir Digby Mackworth, the 3rd Baronet, took the additional surname Dolben after he married Frances, the heiress of Sir John English Dolben, the 4th Baronet.