One of these children was the future Charles I. She often used Scottish politics when she fought with James about her son , Prince Henry . She also used them in her arguments about his treatment of her friend Beatrix Ruthven . The second daughter of King Frederick II of Denmark , Anne married James in 1589 at the age of fourteen and bore him three children who survived infancy , including the future Charles I. She demonstrated an independent streak and a willingness to use factional Scottish politics in her conflicts with James over the custody of Prince Henry and his treatment of her friend Beatrix Ruthven .