Sources

1) Source: Chancery: Inquisitions Post Mortem, Series I, Edward II "WILLIAM DE VESCI of Kildare...Gilbert de Aton is next heir of William de Vescy the elder, for, after the said William’s death without heir of himself, the right of his tenements resorted to one Warin de Vescy as kinsman and heir of his brother, one Eustace, grandfather of the said William the elder on the side of William his father, and from the said Warin the right descended to Margery his daughter and heir, and from her to William her son and heir, and from him to Gilbert his son and heir, and from him, who died without heir of himself, to one William his brother and heir, and from him to the said Gilbert de Aton his son and heir, who is of full age." Date: 1314. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol5/pp307-312. Reference: C 134/40/1 (Data from secondary evidence)