He married Lady Katherine Percy, who was also a great-granddaughter of John of Gaunt by his third wife, Katherine Swynford, and also a descendant of King Edward III of England through his second son, Lionel of Antwerp, 1st Duke of Clarence.

Active militarily in the Wars of the Roses, he especially played a decisive role in the Battle of Northampton by switching his allegiance from the Lancastrian to the Yorkist cause.

For this action he was rewarded by Edward IV with a grant of the manor of Ampthill, ownership of which had come into dispute between Grey, Ralph Lord Cromwell and Henry Holland, Duke of Exeter.

[1] Edmund Grey's appointment as treasurer of England was enacted at Westminster on 24 June 1463 but Walter Blount succeeded him in November 1464.

[3] He was created Earl of Kent on 30 May 1465, shortly after the marriage of his eldest son, Anthony, to the king's sister-in-law, Joan Woodville[1] (she is sometimes known as Eleanor Woodville)[4] He was then appointed chief justice of the county of Meryonnyth, North Wales[5] and constable of Harlech.