Bolko III of Strzelce
Bolko III of Strzelce( also known as of Opole;; – 21 October 1382) was a Duke of Opole during 1356 – 1370( with his brothers as co-rulers) and Duke of Strzelce from 1375 until his death.
He was the second son of Duke Bolko II of Opole by his wife Elisabeth, daughter of Duke Bernard of Świdnica.
Euphrosyne of Opole
Euphrosyne of Opole( and," YefrosiniyaFrosya")( 1228/30 – 4 November 1292) was a daughter of Casimir I of Opole and his wife Viola, Duchess of Opole.
She was a member of the House of Piast and became Duchess of Kujavia from her first marriage and Duchess of Pomerania from her second marriage.
Władysław Opolski
Władysław of Opole( – 27 August/ 13 September 1281/ 2) was a Duke of Kalisz during 1234 – 1244, Duke of Wieluń from 1234 to 1249 and Duke of Opole – Racibórz from 1246 until his death.
He was the second son of Casimir I of Opole by his wife, Viola, probably a Bulgarian lady.
Henry of Opole
Henry of Opole( b. – d.), was a Duke of Opole from 1356 until his death.
He was the third and youngest son of Duke Bolko II of Opole and his wife Elisabeth, daughter of Duke Bernard of Świdnica.
Jan I of Opole
Jan I of Opole  (1410/1413 – 5 September 1439) was a Duke of Opole since 1437 (with his brother as co-ruler).
He was the second son of Duke Bolko IV of Opole by his wife Margareta, possibly member of the House of Görz.
Casimir I of Opole
Casimir I of Opole( – 13 May 1230), a member of the Piast dynasty, was a Silesian duke of Opole and Racibórz from 1211 until his death.
Bolko IV of Opole
Bolko IV of Opole (1363/67 – 6 May 1437), was a Duke of Strzelce and Niemodlin during 1382–1400 (with his brothers as co-rulers), Duke of Opole from 1396 (until 1400 with his brother as co-ruler, except Olesno).
He was the second son of Duke Bolko III of Strzelce by his wife Anna, probably daughter of Duke Jan I of Oświęcim.
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.
Johan Braakensiek
Johan Coenraad Braakensiek( 24 May 1858, Amsterdam – 27 February 1940, Amsterdam) was a Dutch painter, illustrator and political cartoonist.
He is the grandfather of Jan van Oort.
Bolko II of Opole
Bolko II of Opole( before 1300 – 21 June 1356), was a Duke of Opole from 1313( with his brother as co-ruler until 1323).
He was the second son of Duke Bolko I of Opole by his wife Agnes, probably a daughter of Margrave Otto III of Brandenburg.

Question: Who is the paternal grandfather of Jan I Of Opole?
Answer: Bolko III of Strzelce