Question: Who is Siemowit Vi Of Płock's paternal grandfather?

Knowledge 1: Siemowit VI of Płock
Siemowit VI of Płock (pl: "Siemowit VI płocki"; 2 January 1446 - 31 December 1461/1 January 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 eldest son of Władysław I of Płock and Anna, daughter of Duke Konrad V of Oleśnica. [SEP] Knowledge 2: 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.
Knowledge 1: Siemowit VI of Płock
Siemowit VI of Płock (pl: "Siemowit VI płocki"; 2 January 1446 - 31 December 1461/1 January 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 eldest son of Władysław I of Płock and Anna, daughter of Duke Konrad V of Oleśnica. [SEP] Knowledge 2: 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.
Knowledge 1: Siemowit VI of Płock
Siemowit VI of Płock (pl: "Siemowit VI płocki"; 2 January 1446 - 31 December 1461/1 January 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 eldest son of Władysław I of Płock and Anna, daughter of Duke Konrad V of Oleśnica. [SEP] Knowledge 2: Konrad II of Masovia
Konrad II of Czersk( pl:" Konrad II czerski"; c. 1250 – 24 June/ 21 October 1294), was a Polish prince member of the House of Piast, Duke of Masovia during 1264- 1275 jointly with his brother, since 1275 sole ruler over Czersk and Duke of Sandomierz during 1289.He was the eldest son of Siemowit I of Masovia and Pereyaslava, a daughter of Prince Daniel of Halych.

Answer: Siemowit IV