Margaret de Stafford
Margaret Stafford( born c. 1364; died 9 June 1396) was the daughter of Hugh de Stafford, 2nd Earl of Stafford, and Philippa de Beauchamp.
She was the first wife of Ralph Neville, 1st Earl of Westmorland, and the grandmother of the 2nd Earl.
Henry Percy, 8th Earl of Northumberland
Henry Percy, 8th Earl of Northumberland, 2nd Baron Percy( 153221 June 1585) was an English nobleman and conspirator.
Mary of Lancaster
Mary of Lancaster, Baroness Percy (1320 – 1 September 1362), was the youngest surviving child of Henry, 3rd Earl of Lancaster by his wife Maud Chaworth.
Through her father, she was a great-granddaughter of Henry III of England.
Lady Katherine Percy
Lady Katherine Percy( 18 May 1423 –) was the daughter of Henry Percy, 2nd Earl of Northumberland and Lady Eleanor Neville.
Her maternal grandparents were Ralph Neville, 1st Earl of Westmorland and his second wife Joan Beaufort, a legitimized daughter of John of Gaunt.
She married Edmund Grey, 1st Earl of Kent and had seven children:
Richard Percy
Sir Richard Percy( died 1648) was an English soldier who served in Ireland during the 1590s.
He was part of the Percy Family, the son of Henry Percy, 8th Earl of Northumberland and younger brother of Henry Percy, 9th Earl of Northumberland.
Following the outbreak of Tyrone's Rebellion in Ireland, he raised a regiment, of which the majority were drawn from Wales, to supplement the under- strength Irish Army.
The regiment was badly mauled during the Battle of the Yellow Ford in 1598 when, as the advance guard of the relief expedition to a besieged fort on the River Blackwater, they were attacked by Hugh O'Neill, Earl of Tyrone's rebel forces.
Percy's regiment suffered heavy losses in what amounted to a major defeat in which the Marshal of Ireland, Sir Henry Bagenal, was killed.
Thomas Percy, 1st Earl of Worcester
Thomas Percy, 1st Earl of Worcester, KG( 134323 July 1403) was an English medieval nobleman and naval commander best known for leading the rebellion with his nephew Henry Percy, known as' Harry Hotspur', and his elder brother, Henry Percy, 1st Earl of Northumberland.
Dorothy Percy, Countess of Northumberland
Dorothy Percy( née Devereux), Countess of Northumberland( formerly Perrot, née Devereux; c. 1564 – 3 August 1619) was the younger daughter of Walter Devereux, 1st Earl of Essex by Lettice Knollys, and the wife of Henry Percy, 9th Earl of Northumberland.
Henry Percy, 2nd Earl of Northumberland
Henry Percy, 2nd Earl of Northumberland( 3 February 139322 May 1455) was an English nobleman and military commander in the lead up to the Wars of the Roses.
He was the son of Henry" Hotspur" Percy, and the grandson of Henry Percy, 1st Earl of Northumberland.
His father and grandfather were killed in different rebellions against Henry IV in 1403 and 1408 respectively, and the young Henry spent his minority in exile in Scotland.
Only after the death of Henry IV in 1413 was he reconciled with the Crown, and in 1416 he was created Earl of Northumberland.
In the following years, Northumberland occasionally served with the king in France, but his main occupation was the protection of the border to Scotland.
At the same time, a feud with the Neville family was developing, particularly with Richard Neville, Earl of Salisbury.
This feud became entangled with the conflict between the dukes of York and Somerset over control of national government.
The conflict culminated in the first battle of the Wars of the Roses, at St Albans, where both Somerset and Northumberland were killed.
Mary Percy, Countess of Northumberland
Mary Percy, Countess of Northumberland(" née" Talbot; died 16 April 1572) was a courtier and noblewoman during the reign of Henry VIII of England.
She was the daughter of George Talbot, 4th Earl of Shrewsbury.
Her husband, Henry Percy, 6th Earl of Northumberland, had wished to marry Anne Boleyn instead of her.
Henry Percy, 1st Earl of Northumberland
Henry Percy, 1st Earl of Northumberland, 4th Baron Percy, titular King of Mann, KG, Lord Marshal (10 November 134120 February 1408) was the son of Henry de Percy, 3rd Baron Percy, and a descendant of Henry III of England.
His mother was Mary of Lancaster, daughter of Henry, 3rd Earl of Lancaster, son of Edmund, Earl of Leicester and Lancaster, who was the son of Henry III.

Question: Who is the maternal grandmother of Henry Percy, 1St Earl Of Northumberland?
Answer: Maud Chaworth