Son of HAWISE, not Henry, de Grey - and full brother to Walter de Grey, Archbishop of York.

[HAWISE [de Grey] (-after 9 Mar 1240). “Hawisia de Grey vidua” donated “ecclesiam de Cornewell” to Oseney abbey, for the souls of “Johannis de Grey fratris mei quondam Norwicensis Episcopi”, with the consent of “Dni. Roberti de Grey filii et heredis mei”, by undated charter, witnessed by “Dno. Waltero de Grey, Wygorniensi Episcopo filio meo” [which indicates dating to [19 Oct 1214/Feb 16] http://fmg.ac/Projects/MedLands/ENGLISHNOBILITYMEDIEVAL3D-K.htm#_To...

This explicitly identifies Hawise as sister to John, Bishop of Norwich (deceased), and Robert and Walter as her sons.

Received the manor of Rotherfield from his YOUNGER brother Walter, Archbishop of York, who bought it from Eve de Grey (de Murdac de Beauchamp).

Probably the father of Eve de Grey, but primary evidence has not been found.

References

• “Notices relative to the early history of the town and port of Hull;” by Frost, Charles, 1781?-1862 (1827). Page 28-29. Archive.org Note X, page 43. Archive.org