Question: Who is the paternal grandfather of Janusz Iii Of Masovia?

Knowledge 1: Janusz III of Masovia
Janusz III of Masovia (pl: "Janusz III mazowiecki"; ca.27 September 1502 – 9/10 March 1526), was a Polish prince member of the House of Piast in the Masovian branch.He was a Duke of Czersk, Warsaw, Liw, Zakroczym and Nur during 1503-1524 (under regency until 1518) jointly with his brother, and sole ruler during 1524-1526 as the last male member of the Masovian Piasts.He was the second son of Konrad III the Red and his third wife Anna, a daughter of Mikolaj Radziwiłł "the Old", Voivod of Vilnius and the first Grand Chancellor of Lithuania. [SEP] Knowledge 2: Konrad III Rudy
Konrad III the Red(pl: "Konrad III Rudy"; 1447/48 – 28 October 1503), was a Polish prince member of the House of Piast in the Masovian branch.He was a duke of Czersk, Liw, Warsaw, Nur, Łomża, Ciechanów, Różan, Zakroczym and Wyszogród during 1454-1471 jointly with his brothers (under regency until 1462), Duke of Płock, Wizna, Płońsk and Zawkrze during 1462-1471, and after the division of the paternal domains in 1471, sole ruler over Czersk and Liw, over Wyszogród during 1474-1489 and again in 1495, over Zakroczym since 1484, over Nur since 1488 and over Warsaw since 1489.He was the third son of Bolesław IV of Warsaw and Barbara Olelkovna of Slutsk-Kapy, a Lithuanian princess, (granddaughter of Vladimir Olgerdovich).The premature death of his two older brothers during 1453-1454 left him as the eldest surviving son of his family.
Knowledge 1: Siemowit I of Masovia
Siemowit I of Masovia( c. 1224/28 – 23 June 1262), was a Polish prince member of the House of Piast, Duke of Czersk during 1247- 1248, Duke of Masovia( except Dobrzy ń) during 1248- 1262, ruler over Sieradz during 1259- 1260.He was the sixth son of Konrad I of Masovia and his wife Agafia of Rus.He was named after his older brother Siemowit, who died young in 1224. [SEP] Knowledge 2: 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.
Knowledge 1: Konrad III Rudy
Konrad III the Red(pl: "Konrad III Rudy"; 1447/48 – 28 October 1503), was a Polish prince member of the House of Piast in the Masovian branch.He was a duke of Czersk, Liw, Warsaw, Nur, Łomża, Ciechanów, Różan, Zakroczym and Wyszogród during 1454-1471 jointly with his brothers (under regency until 1462), Duke of Płock, Wizna, Płońsk and Zawkrze during 1462-1471, and after the division of the paternal domains in 1471, sole ruler over Czersk and Liw, over Wyszogród during 1474-1489 and again in 1495, over Zakroczym since 1484, over Nur since 1488 and over Warsaw since 1489.He was the third son of Bolesław IV of Warsaw and Barbara Olelkovna of Slutsk-Kapy, a Lithuanian princess, (granddaughter of Vladimir Olgerdovich).The premature death of his two older brothers during 1453-1454 left him as the eldest surviving son of his family. [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.

Answer: Bolesław IV of Warsaw