Tirso de Olazábal, 1st Count of Arbelaiz
Tirso de Olazábal y Lardizábal, 1st Count of Arbelaiz, 1st Count of Oria( 28 January 1842 – 25 November 1921), was a Spanish noble and Carlist politician.
Alfonso XI of Castile
Alfonso XI of Castile (13 August 131126 March 1350), called the Avenger ("el Justiciero"), was the king of Castile, León and Galicia.
He was the son of Ferdinand IV of Castile and his wife Constance of Portugal.
Upon his father's death in 1312, several disputes ensued over who would hold regency, which were resolved in 1313.
Once Alfonso was declared adult in 1325, he began a reign that would serve to strengthen royal power.
His achievements include solving the problems of the Gibraltar Strait and the conquest of Algeciras.
Jean-Frédéric Phélypeaux, Count of Maurepas
Jean-Frédéric Phélypeaux, 1st Count of Maurepas (9 July 1701 – 21 November 1781) was a French statesman and Count of Maurepas.
William Bourchier, 1st Count of Eu
William Bourchier, 1st Count of Eu( 1374- 28 May 1420), was an English knight created by King Henry V 1st Count of Eu, in Normandy.
Francisco de Mascarenhas
Francisco de Mascarenhas was the 1st count of Vila da Horta, the 1st count of Santa Cruz and the 13th viceroy of Portuguese controlled India from 1581 until 1584, captain of donatary of the islands of Flores and Corvo.
Beltrán Alfonso Osorio, 18th duke of Alburquerque
Beltrán Alfonso Osorio y Díez de Rivera, 18th Duke of Alburquerque( 15 December 1918 – 8 February 1994), was a Grandee of Spain and an amateur jockey.
As a Spanish aristocrat, he was known as the" Iron Duke" of Alburquerque.
He was also Duke of Algete, Marquis of Alcañices, los Balbases, Cadreita, Cuéllar, Cullera, and Montaos, Count of Fuensaldaña, Grajal, Huelma, Ledesma, la Torre, Villanueva de Cañedo, and Villaumbrosa.
His son, Juan Miguel Osorio y Bertrán de Lis( b. 1958), is the current Duke of Alburquerque and Duke of Algete.
Henry, Duke of Villena
Infante Henry of Aragon( 1400 – 15 June 1445), 1st Duke of Villena, 4th Count of Alburquerque, Count of Ampurias, was the Grand Master of the Order of Santiago.
Sancho Alfonso, 1st Count of Alburquerque
Sancho Alfonso de Castilla (1342–1374) is known in Spanish as "Don Sancho Alfonso de Castilla, Infante de Castilla, I conde de Alburquerque".
He was the ninth of the ten illegitimate children of King Alfonso XI of Castile and Lady Eleanor de Guzmán.
He was born in Seville.
He participated in a revolt of the Castilian nobles against the despotic rule of his brother, Pedro of Castile.
In 1373 he married Beatrice of Portugal, daughter of Peter I of Portugal and Inês de Castro.
They had two children:
Fernando Sánchez, 2nd Count of Alburquerque, and Eleanor of Alburquerque, who married Ferdinand I of Aragon.
He also had an illegitimate daughter, Leonor Sánchez de Castilla, who married Fadrique de Castilla y Ponce de Leon, illegitimate son of Henry II, King of Castile.
João Afonso Telo, 4th Count of Barcelos
João Afonso
Telo de Menezes( died 1381) was a Portuguese nobleman, 1st Count of Ourém, 1st Count of Viana do Alentejo, and 4th Count of Barcelos.
Beatrice, Countess of Alburquerque
Beatrice of Portugal was Countess of Alburquerque as the wife of Sancho Alfonso of Alburquerque.
She was the daughter of Peter I of Portugal and his wife Inês de Castro.

Question: Who is Sancho Alfonso, 1St Count Of Alburquerque's paternal grandfather?
Answer: Ferdinand IV of Castile