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