Thomas FitzWilliam

The Peerage records that Thomas FitzWilliam lived at Baggotrath, Ireland; Bray, County Wicklow, Ireland; and Merrion, County Dublin, Ireland.

From "A History of the County Dublin: : The People, Parishes and Antiquities from the Earliest Times to the Close of the Eighteenth Century. ... Being a ... County Comprised Within the Parishes of ... " the following text refers to Thomas and his wife Eleanor:

At the end of the fifteenth century the manor of Merrion came into the possession of the branch of the Fitzwilliam family seated on the lands of Dundrum. The latter lands had been assigned in 1365 to William, son of Richard Fitzwilliam, and were at the end of the fifteenth century owned by Thomas Fitzwilliam, the fifth in direct descent from him. In Thomas Fitzwilliam were combined the possession of large property, a liberal education, and high con- nections. When he had come of age in 1486, he had succeeded in addition to the manor of Dundrum to the manor of Baggotrath, and to other lands in the Counties of Dublin and Meath; and in order to fit himself for the care of his estates he went three years later to London to study law. His immediate ancestors had married into the houses of Ferrers, Bellew, and Holywood — all families of importance in the Pale — and to the position and possessions which he inherited he added by his own marriage. His wife, Eleanor, daughter of John Dowdall, was, on her mother's side, a grand-daughter of Sir Jenico Dartasse, a wealthy native of Gascony, a country which in his time passed from English to French rule, who had settled in Ireland and married into one of the old Anglo-Norman families, the Plunketts of Killeen, and ultimately the Fitzwilliams inherited the greater portion of the Dartasse property.

The wikipedia page for his son, William, gives his life span as 1465-1517