Question: What is the date of death of Siemowit Vi Of Płock's father?
Sentence (from "Władysław I of Płock"): 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).
Relevant evidence: No