Peter, Duke of Coimbra
Infante D. Pedro, Duke of Coimbra , (9 December 1392 – 20 May 1449) was a Portuguese "infante" (prince) of the House of Aviz, son of King John I of Portugal and his wife Philippa of Lancaster, daughter of John of Gaunt.
In Portugal, he is better known as Infante D. Pedro das Sete Partidas [do Mundo], "of the Seven Parts [of the World]" because of his travels.
Possibly the best-travelled prince of his time
, he was regent between 1439 and 1448.
He was also 1st
Lord of Montemor-o-Velho, Aveiro, Tentúgal, Cernache, Pereira, Condeixa and Lousã.
John, Prince of Antioch
John, Prince of Antioch (1431–1457), was the second son of Infante Peter, Duke of Coimbra, and Isabella of Urgell, Duchess of Coimbra.
Kaya Alp
Kaya Alp was, according to Ottoman tradition, the son of Kızıl Buğa and the father of Suleyman Shah, who was, in turn, the grandfather of Ertuğrul, and the great grandfather of the Ottoman Empire founder, Osman I.
John Westley
Rev. John Westley( 1636 – 78) was an English nonconformist minister.
He was the grandfather of John Wesley( founder of Methodism).
Theodosius VI of Antioch
Theodosius VI( Abourjaily) of Antioch was Greek Orthodox Patriarch of Antioch from 1958 to 1970.
John I, Prince of Anhalt-Bernburg
John I, Prince of Anhalt- Bernburg( died 5 June 1291) was a German prince of the House of Ascania and ruler of the principality of Anhalt- Bernburg.
He was the eldest son of Bernhard I, Prince of Anhalt- Bernburg, by his wife Princess Sophie, daughter of King Abel of Denmark.
Paul the Jew
Paul the Jew was the Patriarch of Antioch, and head of the Greek Orthodox Church of Antioch, from 519 to 521.
Athanasius I Gammolo
Athanasius I Gammolo was the Patriarch of Antioch, and head of the Syriac Orthodox Church of Antioch from 595 until his death in 631.
Athanasius was also the author of" The Life of Severus of Antioch", a biography of the first Syriac Orthodox Patriarch of Antioch.
John Christian Kunkel
John Christian Kunkel (September 18, 1816 – October 14, 1870) was a Whig and Republican member of the U.S. House of Representatives from Pennsylvania.
He was the grandfather of John Crain Kunkel.
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 the paternal grandfather of John, Prince Of Antioch?
Answer: John I of Portugal