O'Donovan was the guardian to Thomas Fitzgerald, 18th Knight of Glin, known as Tomas Geancach (Thomas Snub-Nosed), who was the eldest son of Gerald (17th) Knight of Glin and his wife, Joan O'Brien, one of the daughters of Donough O'Brien, a chief of Thomond, from CarrigoGlinnell Castle, Co.
Thomas' father Gerald, known as the Knight of the Horses, was killed fighting for James II at the second battle of Windmill Hill after the Siege of Derry in 1689.
As a result, no Williamite received a grant from them, (15) nor were they included in the return made by the inquiry commissioners in 1699.
Thomas was a Jacobite supporter but was probably too young to have played an active part in the war between the two kings.
He was succeeded by 1) Jeremiah, who inherited his estates, but sold the manor in its entirety in 1737 to Richard Tonson.