Bonne of Berry
Bonne of Berry( 1362/1365 – 30 December 1435) was the daughter of John, Duke of Berry, and Joanna of Armagnac.
Through her father, she was a granddaughter of John II of France.
Isabella of Brittany
Isabella of Brittany( 1411 – c. 1444) was a daughter of John V, Duke of Brittany, and his wife, Joan of Valois.
Isabella was a member of the House of Dreux.
John III of Sweden
John III (20 December 1537 – 17 November 1592) was King of Sweden from 1569 until his death.
He was the son of King Gustav I of Sweden and his second wife Margaret Leijonhufvud.
He was also, quite autonomously, the ruler of Finland, as "Duke John" from 1556 to 1563.
In 1581 he assumed also the title Grand Prince of Finland.
He attained the Swedish throne after a rebellion against his half-brother Eric XIV.
He is mainly remembered for his attempts to close the gap between the newly established Lutheran Church of Sweden and the Catholic church.
His first wife was Catherine Jagellonica of the Polish-Lithuanian ruling family, and their son Sigismund eventually ascended both the Polish-Lithuanian and Swedish thrones.
John I, Duke of Cleves
John I, Duke of Cleves, Count of Mark( 16 February 1419 – 5 September 1481) was Duke of Cleves and Count of Mark.
John, Duke of Östergötland
John of Sweden, Duke of Östergötland (in Swedish "Johan")
(18 April 1589 at Uppsala Castle – 5 March 1618 at Bråborg Castle in Östergötland) was a Swedish royal dynast.
He was titular Duke of Finland 1590–1606 and reigning Duke of Östergötland 1606–18.
His father was John III of Sweden and his mother was Gunilla Bielke.
John's half-brother was King Sigismund III of Poland (1566–1632, reigned in Sweden in 1592–99, and in the Polish–Lithuanian Commonwealth in 1587–1632).
His uncle was Charles IX of Sweden, who ruled from 1599 to 1611, and his first cousin was Gustav II Adolf of Sweden (1594–1632).
Charles, Duke of Durazzo
Charles of Durazzo( 1323 – 23 January 1348) was a Neapolitan nobleman, the eldest son of John, Duke of Durazzo and Agnes of Périgord.
Marie, Duchess of Auvergne
Marie of Berry( c. 1375 – June 1434) was" suo jure" Duchess of Auvergne and Countess of Montpensier in 1416- 1434.
She was the daughter of John, Duke of Berry, and Joanna of Armagnac.
She was married three times.
She acted as administrator of the Duchy of Bourbon for her third spouse John I, Duke of Bourbon, during his imprisonment in England after he was captured following the French defeat at the Battle of Agincourt in 1415, until 1434.
John Westley
Rev. John Westley( 1636 – 78) was an English nonconformist minister.
He was the grandfather of John Wesley( founder of Methodism).
Thomas Howard, 2nd Duke of Norfolk
Thomas Howard, 2nd Duke of Norfolk( 144321 May 1524), styled Earl of Surrey from 1483 to 1485 and again from 1489 to 1514, was an English nobleman and politician.
He was the eldest son of John Howard, 1st Duke of Norfolk, by his first wife, Catharina de Moleyns.
The Duke was the grandfather of both Queen Anne Boleyn and Queen Catherine Howard and the great grandfather of Queen Elizabeth I.
He served four monarchs as a soldier and statesman.
Gilbert Talbot, 3rd Baron Talbot
Gilbert Talbot, 3rd Baron Talbot( c. 1332–1387) was an English nobleman and soldier.
He was the grandfather of John Talbot, 1st Earl of Shrewsbury.

Question: Who is John, Duke Of Östergötland's paternal grandfather?
Answer: Gustav I of Sweden