In the fifteenth century both castles came into the possession of the Fitzwilliam family, who became the most substantial landowners in Dublin; James Fitzwilliam, the Chief Baron of the Irish Exchequer, married Sir John Cruises's daughter.
Im 15. Jahrhundert kamen beide Burgen in Besitz der Familie FitzWilliam, die zu den wichtigsten Landbesitzern in Dublin geworden waren; James FitzWilliam, der Chief Baron of the Irish Exchequer, heiratete die Tochter von Sir John Cruise.