Przemysław of Oświęcim
Przemysław of Oświęcim( – 1 January 1406) was a Duke of half of both Głogów and Ścinawa since 1404 and Duke of Oświęcim from 1405 until his death.
He was the eldest son of Przemysław I Noszak, Duke of Cieszyn by his wife Elisabeth, daughter of Bolesław, Duke of Koźle- Bytom.
In the chronicle of Jan Długosz he is named the second son, but this is certainly a mistake, because elsewhere, he was always placed in first place before his brother Bolesław I.
Jan III of Oświęcim
Jan III of Oświęcim( 1366 – by 19 August 1405) was a Duke of Oświęcim since 1376 until his death.
He was the eldest child and only son of Duke Jan II of Oświęcim by his wife Hedwig, daughter of Ludwik I the Fair, Duke of Brzeg.
Initially, historians thought that Dukes Jan II and Jan III are the same person, until the discovery of further sources who confirmed Jan III's existence.
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.
Barbara of Karniów
Barbara of Karniów( 1445 – April 27, 1510) was the daughter of Nicholas V of Karniów and Margaret Clemm of Ellguth.
In 1475 she married Jan IV of Oświęcim.
Together they had one daughter Helena( b. 1478/80 – d. aft. 1524), married in 1492 to Baron George of Schellenberg
Helena of Oświęcim
Helena of Oświęcim( 1478/80 – after 1524), was a Polish princess member of the House of Piast from the Oświęcim branch and ruling Duchess of Karniów since 1506 until 1523.
She was the only child of Duke Jan IV of Oświęcim by his second wife Barbara, daughter of Duke Nicholas V of Karniów.
Jan I the Scholastic
Jan I the Scholastic( 1308 /10 – 1372 before 29 September), was a Duke of Oświęcim from 1324 until his death.
He was the eldest child and only son of Duke Władysław of Oświęcim by his wife Euphrosyne, daughter of Duke Boleslaus II of Masovia.
Władysław of Oświęcim
Władysław of Oświęcim( 1275/80 – by 15 May 1324), was a Duke of Oświęcim from 1315 until his death.
He was the eldest son of Mieszko I, Duke of Cieszyn by his wife, probably called Grzymisława.
Casimir I of Oświęcim
Casimir I of Oświęcim  (1396 – 7 April 1434) was a Duke of Oświęcim since 1406 (under regency until 1414), ruler over Toszek (from 1414) and Strzelin (during 1416–1427).
He was the only child of Duke Przemysław of Oświęcim by his unknown wife.
Jan IV of Oświęcim
Jan IV of Oświęcim (1426/1430 – by 21 February 1497), was a Duke of Oświęcim during 1434–1456 (until 1445 with his brothers as co-rulers) and Duke of Gliwice from 1465 to 1482.
He was the third son of Duke Casimir I of Oświęcim by his first wife Anna, daughter of Duke Henry VIII of Żagań.
Jan II of Oświęcim
Jan II of Oświęcim( – 19 February 1376) was a Duke of Oświęcim since 1372 until his death.
He was the only son of Jan I the Scholastic, Duke of Oświęcim, by his unknown first wife.

Question: Who is Jan Iv Of Oświęcim's paternal grandfather?