Question: What is the date of death of Bogusław Fryderyk Radziwiłł's mother?
Sentence (from "Bogusław Fryderyk Radziwiłł"): His mother was Princess Louise of Prussia, and through her, he was great-grandson of King Frederick William I of Prussia, great-great-grandson of King George I of Great Britain, cousin of William I, German Emperor and Tsar Alexander II of Russia.
Relevant evidence: Yes