In 1896 Dr. John Lumsden married Caroline Frances Kingscote, daughter of Major Fitzhardinge Kingscote and Agnes Grant Stuart, and their first child, John Fitzhardinge Lumsden, was born on 11 June 1897.
Their first child was soon followed by sisters: Leslie, born in 1898, Norah in 1900, Margery in 1908 and twins, Nancy and Betty born in 1911.