Euphemia of Masovia
Euphemia of Masovia( 1395/97 – before 17 September 1447), was Duchess of Cieszyn by marriage to Bolesław I, Duke of Cieszyn, and regent of the Duchy of Cieszyn during the minority of her sons from 1431.
She was the third daughter of Siemowit IV, Duke of Masovia and Alexandra, daughter of Algirdas, Grand Duke of Lithuania and sister of King Władysław II Jagiełło of Poland, and thus a Polish princess member of the House of Piast in the Masovian branch.
Sophia of Masovia
Sophia of Masovia( 1497/1498- before 11 March 1543) was a Princess of Masovia, daughter of Konrad III Rudy, Duke of Masovia and his wife Anna Radziwiłł.
She was a member of the House of Piast.
On 17 September 1520 in Warsaw, Sophia was married by proxy to Stephen VII Báthory.
On 17 January 1521, Sophia and her entourage went to Hungary, where in February there was a formal marriage.
The couple had three children:
Anna, Stephen and Klara; however, other sources claim that Klara was the couple's only child.
Klara was engaged to Carl, Duke of Münsterberg, but died in 1535, before the marriage took place.
After the death of Stephen in 1530, Sophia was married to Croatian magnate Louis Pekry.
Sophia's second marriage was childless.
She then died sometime before 11 March 1543.
Sophia had three siblings: Stanislaus I of Masovia, Janusz III of Masovia and Anna of Masovia, both her brothers died childless and so Anna and Sophia were the last Masovian Piasts.
Soon after Janusz's death, the Duchy of Masovia was annexed into the kingdom of Poland, despite resistance from some of the Masovian nobility.
They tried to retain their independence and argued that the Duchy should be inherited by the female relatives( such as Anna or Sophia).
The Polish king refused to recognize their demands.
Anna was made titular Duchess of Masovia.
Hedwig of Masovia
Hedwig of Masovia( ca. 1392 – after 19 February 1439), was a Polish princess, member of the House of Piast in the Masovian branch.
She was the eldest daughter of Siemowit IV, Duke of Masovia and Alexandra, a daughter of Algirdas, Grand Duke of Lithuania and sister of King Władysław II Jagiełło of Poland.
Władysław I of Płock
Władysław I of Płock (pl: "
Władysław I płocki"; 1406/09 - 11/12 December 1455), was a Polish prince member of the House of Piast from the Masovian branch.
He was a Duke of Płock, Rawa Mazowiecka, Gostynin, Sochaczew, Belz, Płońsk, Zawkrze and Wizna during 1426-1434 jointly with his brothers, after the division of the paternal inheritance between him and his brothers in 1434, sole ruler over Płock, Płońsk, Wizna and Zawkrze; in 1442 he reunited all their patrimony (except Gostynin).
He was the fifth son of Siemowit IV, Duke of Masovia and Alexandra of Lithuania, daughter of Algirdas.
Amelia of Masovia
Amelia of Masovia( pl:" Amelia mazowiecka"; 1397/98- after 17 May 1434), was a Polish princess member of the House of Piast in the Masovian branch.
She was the fourth daughter of Siemowit IV, Duke of Masovia and Alexandra, a daughter of Algirdas, Grand Duke of Lithuania and sister of King Władysław II Jagiełło of Poland.
Władysław II of Płock
Władysław II of Płock (pl: "Władysław II płocki";
aft.
31 October 1448 - 27 February 1462), was a Polish prince member of the House of Piast from the Masovian branch.
He was a Duke of Płock, Rawa Mazowiecka, Belz, Płońsk, Zawkrze and Wizna during 1455-1461/62 (under regency until 1459) jointly with his brother, since 1459 ruler over Gostynin.
He was the second son of Władysław I of Płock and Anna, daughter of Duke Konrad V of Oleśnica.
Siemowit III, Duke of Masovia
Siemowit III of Masovia( his name also rendered Ziemowit; – 1381) was a prince of Masovia and a co-regent( with his brother Casimir I of Warsaw) of the lands of Warsaw, Czersk, Rawa, Gostynin and other parts of Masovia.
Catherine of Masovia
Catherine of Masovia( pl:" Katarzyna mazowiecka"; 1413/16 – betw.
2 June 1479/5 July 1480) was a Polish princess member of the House of Piast in the Masovian branch.
She was the eighth and youngest daughter of Siemowit IV, Duke of Masovia and Alexandra, a daughter of Algirdas, Grand Duke of Lithuania and sister of King Władysław II Jagiełło of Poland.
Anna of Masovia
Anna of Masovia( c. 1498 – after 26 January 1557 in Jaroslaw) was Princess of Mazovia and a member of the House of Piast.
She was the last representative of the line of Masovian- Piast.
She was the second daughter of Konrad III of Masovia and Anna Radziwiłł.
She was a sister of Dukes Janusz III of Masovia and Stanislaus of Masovia, and Sophia, who married Stephen VII Báthory.
Kunigunde of Bohemia
Kunigunde of Bohemia( January 1265 – 27 November 1321) was the eldest daughter of Ottokar II of Bohemia and his second wife, Kunigunda of Slavonia.
She was a member of the Přemyslid dynasty.
She was Princess of Masovia by her marriage to Boleslaus II of Masovia and later became abbess of the St. George's Convent at Prague Castle.

Question: Who is the paternal grandfather of Władysław Ii Of Płock?
Answer: Siemowit IV