Kathleen was the third and youngest of the couple's children, following a sister and a brother; when she was two the family moved to Blackburn, after William was appointed headmaster of St Paul's School in the town.
Kathleen foi a terceira e máis nova dos fillos da parella, seguindo a unha irmá e a un irmán; cando ela tiña tan só dous anos a familia trasladouse a Blackburn, logo de que William fora nomeado director da St Paul's School da cidade.