When Jones was nine and a half years old, she moved in with the Beaumont family because she was to be wed to one of their sons, Sapcott Beaumont. When she was thirteen, Beaumont's father died; this event caused the marriage arrangements between the couple to dissolve. She moved back home and two years later married Arthur Jones, heir to Viscount Ranelagh at the age of 15 and she became known as Katherine Jones. It was common for noble women to get married at a younger age, but normally women of this time would not get married until their twenties. As evidenced through letters to her father from her husband, it is insinuated that Arthur Jones was unfaithful to her. Their marriage was not a good one. They spent most of their time living apart, Katherine moving back and forth between Ireland and London, and Arthur spending much of his time travelling. They had three daughters and one son: Catherine, Elizabeth, Frances, and Richard. Katherine lived in Ireland until 1642 when she was trapped in Athlone Castle for four months due to the rebellions in Ireland. Frustrated, she moved to London with her four children in tow.