Sources

1) 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)
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 secondary evidence)
3) 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
4) Source: Chancery: Inquisitions Post Mortem, Series I, Henry IV "Ankaret wife of Thomas Nevyll (Neville), knight, and widow of Richard Talbot, knight: Wiltshire (assignment of dower)...She died on 1 June last. Gilbert Talbot, knight, her son and heir, is aged 24 years and more...Gilbert Talbot, knight, of Goodrich Castle formerly held the manors of Longhope, Huntley and Lydney and 2 parts of the manor of Leigh in his demesne as of fee and granted them to Richard and Ankaret his wife and the heirs of their bodies. They held them and had issue Gilbert Talbot, knight, Richard died and Ankaret held them whilst she lived...She held in her demesne as of fee half the manor of Badgeworth of Humphrey son and heir of Edmund earl of Stafford, a minor in the king’s ward,"Dated: 9 June 1413. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol20/pp30-49. Reference: C 137/33/61 (Data from secondary evidence)