sentences:  The castle, along with Killeen Castle, was held by the Cusacks, initially on behalf of the de Lacys, and passed by marriage in the early 15th century to the Plunketts.Originally, it and Killeen lay on a single estate but the first generation of Plunketts gave Killeen to the eldest son, and Dunsany to the younger, Christopher, following which the estate was divided, and the Castle descended in the hands of the Barons of Dunsany, who enjoyed almost uninterrupted ownership and control, aside from issues around Oliver Cromwell's operations in Ireland (the then Lady Dunsany defended the castle against an initial approach but the family were later forced out, some dying on the way to Connaught), and the aftermath of some other troubles between Ireland and England.They were cousins of Saint Oliver Plunket.