Sources

1) Source: Special Collections: Ancient Petitions "Richard Talbot, son of Gilbert Talbot, and Elizabeth Talbot, his wife."Dated: c1328. External Link
http://discovery.nationalarchives.gov.uk/details/r/C9682494. Reference: SC 8/310/15484 (Data from direct source)
2) Source: Chancery: Inquisitions Post Mortem, Series I, Edward III "Gilbert Talbot or Talebot...He died on Friday, 24 February, 20 Edward III. Richard Talebot, aged 40 years, is his next heir...Thomas, with the king’s licence, granted the same to the said Richard and Elizabeth"Dated: 1346. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol8/pp518-525. Reference: C 135/82/18 (Data from direct source)
3) Source: Chancery: Inquisitions Post Mortem, Series I, Edward III "Mary de Sancto Paulo (St Pol), countess of Pembroke, late wife of Aymer (Emard) de Valence...She died on 16 March last. Gilbert Talbot, aged 30 years and more, is next heir of the said Thomas, to wit, son of the said Richard son of Gilbert Talbot brother of the said Thomas...he reversion thereof was assigned to Elizabeth Comyn, kinsman and one of the heirs of the said earl, who was afterwards taken to wife by Richard Talbot, and three years ago Gilbert Talbot, Elizabeth’s son and heir...Gilbert Talbot, aged 36 years and more"Dated: 1377. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol14/pp330-340. Reference: C 135/262/1 (Data from direct source)
4) Source: Chancery: Inquisitions Post Mortem, Series I, Edward I "Richard Talebot, alias Tallebot, Talbot, Thalebot...Gilbert his son, aged 29 on the feast of St. Luke last, is his next heir."Dated: 3 September 1306. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol4/pp238-249. Reference: C 133/122/10 (Data from direct source)