John, Prince of Portugal (1451)
John, Prince of Portugal was a Portuguese infante, son of Afonso V and Isabella of Coimbra.
He was born heir to the throne in 1451, but he died young during the same year.
The title of Prince of Portugal then passed again to Infante Ferdinand, Duke of Viseu, his uncle.
João, Duke of Viseu
Infante João of Viseu( c. 1448 1472) was the older son of Infante Fernando, Duke of Viseu and of his wife Infanta Beatrice of Portugal.
In 1470, following his father's death, he inherited the titles of Duke of Viseu and Duke of Beja, as well as the Lordships of Covilhã and Moura.
He also became Master of the Order of Christ and of the Order of Santiago, becoming also Constable of Portugal.
In July 1472, his uncle, King Afonso V granted him the Moroccan city of Anfa( in Portuguese" Anafé").
He died young and single, without issue.
His brother, Infante Diogo, inherited his titles and estates.
Diogo, Duke of Viseu
Infante Diogo of Viseu( 1450 – 1484) was the second son of Ferdinand, Duke of Viseu, and his wife Beatriz, Duchess of Viseu.
Dinis of Braganza, Count of Lemos
Dinis of Braganza( 1481 – 1516) was the younger son of Fernando II, Duke of Braganza and Isabella of Viseu who was a daughter of Infante Fernando, Duke of Viseu and Beatrice of Portugal.
Ferdinand, Duke of Viseu
Infante Ferdinand, Duke of Viseu and Beja (or "Fernando," , 1433 – 1470) was the third son of Edward, King of Portugal and his wife Eleanor of Aragon.
Infante Miguel, Duke of Viseu
Infante Dom Miguel, Duke of Viseu( born 3 December 1946) is a member of the Portuguese royal family, as the second child of Duarte Nuno, Duke of Braganza, and Princess Maria Francisca of Orléans- Braganza.
The Duke of Viseu is fourth in the Line of succession to the former Portuguese throne, behind his elder brother, Duarte Pio, Duke of Braganza, and his three children.
The Duke of Viseu is a noted patron of the arts and painter, and the founder and sponsor of the annual Luso- Brazilian Week of Aldravist Art, held interchangeably between Portugal and Brazil.
He is also an active member in various orders of chivalry, notably the Sovereign Military Order of Malta and the Sacred Military Constantinian Order of Saint George.
João de Lencastre, 1st Duke of Aveiro
João de Lencastre(?, 1501 – Coimbra, 1571), was the older son of Infante George, Duke of Coimbra and of his wife" Dona" Beatriz of Vilhena.
Through his father, John was a grandchild of King John II of Portugal and a 3rd cousin to King Manuel I of Portugal.
Through his mother, daughter of Álvaro of Braganza( 4th male son of Fernando I, 2nd Duke of Braganza), John of Lencastre was close related to the most prestigious aristocratic families of the Kingdom( namely the Duke of Braganza, the Marquis of Ferreira, the Marquis of Vila Real, the Count of Vimioso, the Count of Portalegre).
When he was 12 years old, he served crown prince John( who became later King John III of Portugal) and King Manuel I granted him the title of Marquis of Torres Novas by a royal decree issued on March 27, 1520.
In that time, the royal house announced the marriage of Infante Ferdinand, Duke of Guarda( King Manuel I younger son) to the richest and prestigious heir" Dona" Guiomar Coutinho, 5th Countess of Marialva and the 3rd Countess of Loulé.
However, John of Lencastre declared he had secretly married the richest bride.
The scandal in the Court ended when King John III ordered the Marquis imprisonment in the Castle of São Jorge, in Lisbon, allowing the celebration of the Infante Ferdinand's marriage.
After nine years, when he was released, he went to live in Setúbal, maybe ashamed for the situation, and he only returned to the Court in 1535, to escort Infante Luis, Duke of Beja, who was leading the Portuguese fleet in Charles V ’s crusade against Tunis.
In that year King John III granted him the title of Duke of Aveiro.
After his return from Madrid, in 1537( where he was sent by King John III to present formal condolences to Charles V, when his wife, Empress Isabel of Portugal, died) John of Lencastre, 1st Duke of Aveiro, decided to marry to" Dona" Juliana de Lara, daughter of the 3rd Marquis of Vila Real.
In 1552, he was again chosen by the King to escort, from the border to Lisbon, the Infanta Joan of Spain, who would marry John, Crown Prince of Portugal( John III only surviving son).
John of Lencastre and Juliana de Lara had two sons: John of Lencastre wrote several books and built a magnificent convent in Arrábida, near Setúbal, where an annual music festival takes place.
Isabel of Viseu
Isabel of Viseu( 1459 – 1521) was a daughter of Infante Fernando, Duke of Viseu and his wife and cousin Infanta Beatrice, Duchess of Viseu.
She was a member of the House of Aviz and later, House of Braganza.
Edward, King of Portugal
Duarte (31 October 1391 – 9 September 1438), known in English as Edward and called the Philosopher ("o Rei-Filósofo") or the Eloquent ("o Eloquente"), was King of Portugal from 1433 until his death.
He was born in Viseu, the son of John I of Portugal and his wife, Philippa of Lancaster.
Edward was the oldest member of the "Illustrious Generation" of accomplished royal children who contributed to the development of Portuguese civilization during the 15th century.
As a cousin of several English kings, he became a Knight of the Garter.
Frederick Charles Ferdinand, Duke of Brunswick-Lüneburg
Frederick Charles Ferdinand, Duke of Brunswick- Lüneburg( 5 April 1729 in Brunswick – 27 April 1809 in Glücksburg), was a member of the House of Guelph.
he was a Danish field marshal and also the last Duke of Brunswick- Bevern.

Question: Who is the paternal grandfather of Ferdinand, Duke Of Viseu?
Answer: John I of Portugal