Research Notes:
The Oxford Dictionary of National Biography states, [1]
Seagrave [Segrave], Nicholas of, first Lord Seagrave (1238?–1295), baron, was the son of the justice Gilbert of Seagrave (d. 1254) and his wife, Amabilia, ultimately the sole heir of Robert of Chalcombe, and grandson of the justiciar Stephen of Seagrave. Following Gilbert's death in 1254 his lands were granted to Henry III's son Edward, allowing provision for the widow's dower; Nicholas, the heir, was described as sixteen or seventeen years old.
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Seagrave's wife, Matilda, was probably a member of the Lucy family. On 26 August 1288 a commission of oyer and terminer was appointed to hear the complaint of Nicholas of Seagrave the elder and Matilda his wife that forty-six named persons of both sexes had assaulted Matilda at Exhall, Warwickshire, thrown her out of her carriage, and taken away her long cart laden with victuals and other goods. The Song of Caerlaverock attributes five sons to Seagrave; the eldest of these was John Seagrave, variously described as over thirty and (more reliably) thirty-nine at his father's death. The second son was Nicholas Seagrave, lord of Stowe. The elder Nicholas had died by 12 November 1295, and John had done homage for his father's lands by 10 December 1295.
[1] Helen M. Jewell, "Seagrave [Segrave], Nicholas of, first Lord Seagrave (1238?-1295)," Oxford Dictionary of National Biography (Oxford University Press, 2004, online edition), [Oxford_Dictionary_National_Biography], [OxfordDNB(UM)].