Question: Wilhelmine Schröder was the royal mistress of a man that was King of Sweden beginning in what year?
Sentence (from "Wilhelmine Dorothee von der Marwitz"): Wilhelmine Dorothee von der Marwitz (April 1718-16 January 1787), was the royal mistress of Frederick, Margrave of Brandenburg-Bayreuth, from the late 1730s until 1744.
Relevant evidence: No