FitzGerald, Gerald fitz Maurice (c.1150–1204), lord of Offaly, second son of Maurice fitz Gerald (qv), and ancestor of the earls of Kildare, formed the basis of the lineage's landed wealth during his lifetime. He was present with his father at the siege of Dublin by Ruaidrí Ua Conchobair (qv), king of Connacht, in 1170 and took part in the surprise attack that routed Ua Conchobair's army. After his father's death (September 1176), his elder brother, William, granted him half of their father's cantred, giving him a lordship centred on Maynooth, which became the family's caput. William's possession of Naas and Gerald's of Maynooth were later confirmed by John (qv), then lord of Ireland, in 1185. However, the brothers could not retain their father's custody of Wicklow, which was taken from them by the justiciar, William fitz Audelin (qv), in 1177, although they were granted Ferns as a partial recompense. Fitz Maurice came to hold lands around Youghal when he inherited the lands of his younger brother, Alexander. He also received lands around Croom (Co. Limerick), when the kingdom of Thomond was partitioned among the Anglo-Normans. His marriage to Eva, one of the coheiresses of Robert de Bermingham, brought the manors of Lea and Geashill, and he was recognised as lord of Offaly. His possession of these manors was challenged in 1199 by Maurice fitz Philip, but he retained possession till his death in 1204, when his lands passed to his 9-year-old son, Maurice (qv) (d. 1257).
Giraldus, Expugnatio; CDI; G. H. Orpen, ‘The Fitz Geralds, barons of Offaly’, R.S.A.I. Jn., 6th ser., iv (1914), 99–113; Marie Therese Flanagan, Irish society, Anglo-Norman settlers, and Angevin kingship (1987)