On her mother's death Lady Katherine's elder sister, Lady Rosamund Agnes (1914–2003) became the 11th Countess of Dysart, but never married or had issue; on her death in December 2003 Lady Katherine succeeded to the titles of Countess of Dysart and Lady Huntingtower.
Lady Rosamund Agnes (1914–2003), as Lady Katherine's elder sister and the 11th Countess of Dysart, succeeded to the title upon her mother's death but remained unmarried and childless. In December 2003, after Lady Rosamund's passing, Lady Katherine inherited both the titles of Countess of Dysart and Lady Huntingtower.