Key Facts

Parents:	16812994William de Say Her mother's identity is uncertain.
Born:	roughly circa 1252 location unknown
Died:	unknown
Buried:	unknown

Although no contemporary document explicitly says so, 8406497Agnes is surely the daughter of 16812994William de Say. (Evidence: [1] 16812994William owned a manor at Streat, Sussex,1 which 8406497Agnes' husband 8406946Alexander later owned.2 [2] 16812994William had a son named William,1 and this son William served in the military with 8406946Alexander in 1276.3)

8406497Agnes' mother may have been 16812994William de Say's first wife, Sibyl ___4 (Indeed, Douglas Richardson's Royal Ancestry asserts that this is so.5), but I don't understand which contemporary evidence, if any, allows for such a conclusion.

8406497Agnes' brother William was born circa 1252 (On 20 November 1271, he was either 18 or 19 years old.1), so we can surmise that 8406497Agnes was born around roughly the same time.

8406497Agnes married 8406496Alexander de Cheyne. Their son 4203248William was born circa 1274.2

Sources Cited:

1: Calendar of Inquisitions Post Mortem and Other Analogous Documents Preserved in the Public Record Office, Volume I, Henry III (London, 1904), pages 281-282.

2: Calendar of Inquisitions Post Mortem and Other Analogous Documents Preserved in the Public Record Office, Volume III, Edward I (London, 1912), page 205-6.

3: Calendar of the Patent Rolls Preserved in the Public Record Office: Edward I, 1272-1281 (London, 1901), page 156.

4: John Thorpe, ed., Registrum Roffens: or, A Collection of Antient Records, Charters, and Instruments of Divers Kinds [...] of the Diocese and Cathedral Church of Rochester (London, 1769), page 169. The key phrases are "Willelmus de Sai" and "uxoris mee Sibille."

5: Douglas Richardson, Royal Ancestry: A Study in Colonial and Medieval Families, 2nd edition, (Salt Lake City, Utah, 2013), volume IV, page 565.