"Magdalene Sibylle of Brandenburg-Bayreuth (27 October 1612 – 20 March 1687) was Electress of Saxony from 1656 to 1680 as the wife of John George II. The daughter of Christian, Margrave of Brandenburg-Bayreuth, and Marie of Prussia, she was by birth a Markgräfin, or Margravine, and a member of the Brandenburg-Bayreuth branch of the House of Hohenzollern.
Born in Bayreuth, she was her parents´ fifth child. Her maternal grandparents were Albert Frederick, Duke of Prussia, and Marie Eleonore of Cleves. One of her maternal aunts was Duchess Anna of Prussia. She had three surviving siblings: Anna Maria (1609–1680), wife of Prince Johann Anton I von Eggenberg, Duke of Krumlov; Erdmann August (1615–1651); and George Albert (1619–1666)." - (en.wikipedia.org 01.02.2020)