Sources

1) Source: Chancery: Inquisitions Post Mortem, Series I, Edward III "JOHN DE FERRARIIS, knight...He died on 31 March, 41 Edward III. Robert de Ferrariis, his son, aged 7 years and more, is his heir...Broghton. The manor, held in right of Elizabeth his wife, who survives. Elizabeth holds it for life as jointly enfeoffed with one Fulk Lestrange, her former husband, deceased, the reversion belonging to the heirs of John Lestrange, father of Fulk. The manor is not held of the king, but of whom else it is held the jurors know not.He died on 3 April last. Robert, son of the aforesaid John and Elizabeth, aged 7 years and more, is his heir." Date: 1367. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol12/pp105-118. Reference: C 135/193/13 (Data from direct source)
2) Source: Chancery: Inquisitions Post Mortem, Series I, Edward III "John de Bures...held for his life of the inheritance of John son and heir of Robert de Ferrers...He died on 21 December last. Katharine his daughter, wife of Giles de Bello Campo, aged 26 years and more, is his heir...He died on the feast of St. Thomas the Apostle last. Heir as above, aged 35 years and more...He died on 21 December last. Heir as above, aged 30 years and more...He died on 6 December...John son of Robert de Ferrar’, aged 19 years, is heir of the said Hawise de Ferres."Dated: December 1350. External Link
http://discovery.nationalarchives.gov.uk/details/r/C9777688. Reference: C 135/110/8 (Data from secondary evidence)
3) Source: Main Ferrers Estate "Consists of...Copy of a writ of Non Omittas for...husband of Elizabeth, dau. of Thomas the brother of John Bermyngham for possession of property...for possession for Edmund son of Robert."Dated: 1425-1425. External Link
http://discovery.nationalarchives.gov.uk/details/r/abccbe0f-d255-450a-96c1-4b8f1c211d67. Reference: 26D53/1584 (Data from direct source)