From "Complete Peerage England, Scotland, Ireland, Great Britain" by George E Cokayne, CS421.G2 1982, vVII, p200: he died 1203, was 1st Baron Offaly by his marriage.
From "Complete Peerage England, Scotland, Ireland, Great Britain" by George E Cokayne, CS421.G2 1982, v IV, page 233, Desmond:
John FitzThomas, son and heir of Thomas FitzMaurice (who died in 1213 or 1214), by Sabina or Sadhbh, his wife. The younger son of Morice fitz Gerald, one of the conquerors of Ireland, his elder brothers being William of Naas, and Gerald of Offaly.
Weis' "Ancestral Roots. . ." (178:4), he was 1st Baron of Offaly, was at the seige of Dublin, 1171.
Took part in conquest of Limerick about 1197, grantee of Croom there. Ancestor of Earls of Kildare and Dukes of Leinster.
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