From Wikipedia, “Nicholas de Segrave, 1st Baron Segrave”

Nicholas de Segrave (or Seagrave), 1st Baron Segrave (c. 1238 – 1295) was an English baronial leader. Nicholas was grandson of Stephen de Segrave.[2]
Segrave was one of the most prominent baronial leaders during the reign of King Henry III. In 1295 he was summoned to Parliament as Baron Segrave (some sources claim that he was summoned already in 1283). He died by 12 November of the same year and was succeeded in the barony by his son John.
Marriage and issue
By his wife Matilda (Maud) de Lucy, daughter of Sir Thomas de Lucy of Copeland and Isabel de Bolteby, daughter of Adam Nicholas de Bolteby. Nicholas and Matilda had;
• John Segrave, 2nd Baron Segrave, married Catherine de Plessy and had descendants
• Simon Segrave
• Gilbert Segrave, Bishop of London
• Eleanor, married to Alan la Zouche, 1st Baron la Zouche of Ashby and had descendants.
• Nicholas Seagrave, was a soldier and administrator, and lord of Stowe in Northamptonshire. From 1308 to 1316 he was Lord Marshal of England. He died in 1321.[3]
• Henry Segrave
• Geoffrey Segrave

References
1. Some Feudal Coats of Arms and Pedigrees. Joseph Foster. 1902. (p.115)

2. Stourton, A.J. (1876) 5 papers relating to ... Mowbray and Segrave Oxford University pg 17 (via Google)

3. J. S. Hamilton, Nicholas Seagrave, Oxford Online Dictionary of National Biography, 2004

Further reading
• Helen M. Jewell, Nicholas of Seagrave, first Lord Seagrave, Oxford Online Dictionary of National Biography, 2004
• Kidd, Charles, Williamson, David (editors). Debrett's Peerage and Baronetage (1990 edition). New York: St Martin's Press, 1990.