Sources

1) Source: Special Collections: Ancient Petitions "John de Segrave; Margaret de Segrave, wife of John de Segrave and daughter and heir of Thomas de Brotherton; Edward de Mountagu (Montacute); Alice de Montacute, wife of Edward de Montacute and daughter and heir of Thomas de Brotherton."Dated: 1345. Reference: SC 8/278/13878 (Data from secondary evidence)
2) Source: Chancery: Inquisitions Post Mortem, Series I, Henry IV "Thomas Moubray, earl Marshal...He held the manors of Bosham and Stoughton in fee tail by the grant of Edward II to Thomas de Brotherton, his brother, of the lands of Roger le Bygod, sometime earl of Norfolk and Marshal [CChR 1300–26, pp.205–6]. They descended to Margaret duchess of Norfolk as daughter and heir of Thomas, from her to Thomas de Moubray, duke of Norfolk, as son of Elizabeth, daughter of Margaret, and so to Thomas as son of Thomas Moubray, and now to John Moubray as brother and heir... Thomas as son of Thomas duke of Norfolk, son of Elizabeth, daughter of John de Segrave and Margaret; and so now to John de Moubray as brother and heir. "Dated: 1407. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol19/pp101-120. Reference: C 137/62/76 (Data from direct source)
3) Source: Chancery: Inquisitions Post Mortem, Series I, Henry IV "Thomas Moubray (Mowbray), earl Marshal...John Moubray, his brother and heir...He held the manors of Bosham and Stoughton in fee tail by the grant of Edward II to Thomas de Brotherton, his brother, of the lands of Roger le Bygod, sometime earl of Norfolk and Marshal [CChR 1300–26, pp.205–6]. They descended to Margaret duchess of Norfolk as daughter and heir of Thomas, from her to Thomas de Moubray, duke of Norfolk, as son of Elizabeth, daughter of Margaret, and so to Thomas as son of Thomas Moubray, and now to John Moubray as brother and heir...to William de Brewosa, senior, with remainder to John de Moubray and Aline his wife and their heirs. From them they descended to John their son, John his son, to Thomas duke of Norfolk, his son and heir, to Thomas the Earl Marshal, and now to John his brother...7 messuages and 10 bovates in Epworth, Haxey, and Owston in the Isle of Axholme, which John Lord Moubray, son of John, son of Roger"Dated: 1407. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol19/pp101-120. Reference: C 137/62/76 (Data from direct source)
4) Source: The Mowbray Estate "Whereas John de Segrave has granted to John de Moubray an annual rent of £300 from his lands in Leicestershire, and another of £200 from his lands in Huntingdonshire, and one of £100 from his lands in Warwickshire, by three charters, John de Moubray has granted that if John de Segrave enfeoffs John son of John de Moubray and Elizabeth his wife of £100 of land and rent for Elizabeth's life, and the same to them for their joint lives, the charters granting the rents of £600 a year will be void." Agreement of marriage terms for his daughter Elizabeth.. External Link
http://discovery.nationalarchives.gov.uk/details/r/ea0f9c6a-6581-4a64-bf60-cc1361a1a03b. Reference: BCM/D/1/1/13 (Data from direct source)
5) Source: The Mowbray Estate "John lord of Segrave; and John son of John lord of Moubray and Elizabeth his wife. 16 Aug. 23 Edw. IIIJohn de Segrave has granted to John and Elizabeth, for Elizabeth's life, a rent of 66s. 8d. from his manor of Diseworth (Leics.).". External Link
http://discovery.nationalarchives.gov.uk/details/r/54e5178c-ec3d-4f85-bfef-b54a545bf123. Reference: BCM/D/1/1/14 (Data from secondary evidence)