William was a younger son of Pierre de Grandison and Agnes Neufchâtel. He was the younger brother of a key ally and envoy, for King Edward I of England, Otto de Grandson, Grandison being an anglicisation of Grandson.
^ a b c d eWilliams, David (June 2018). "The First Marriage and Issue of William de Grandison, 1st Lord Grandison". Foundations. 10: 89–97.
^ a b c d e f g h i j kGurney, Daniel (1845). The record of the house of Gournay. Oxford: Oxford University. p. 149.
References
Burke, John Bernard (1866). A Genealogical History of the Dormant: Abeyant, Forfeited, and Extinct Peerages of the British Empire. London: Harrison. OCLC 457204792.