The latter became Duke of Prussia after Albert Frederick's death in 1618.
Sigismund II was also Albert Frederick's cousin.
In 1594, Albert Frederick's then 14-year-old daughter Anna married the son of Joachim Frederick of Hohenzollern-Brandenburg, John Sigismund.
The Electors of Brandenburg inherited the Duchy of Prussia upon Albert Frederick's death in 1618, but the duchy continued to be held as a fief under the Polish Crown until 1656/7. Since John Sigismund had suffered a stroke in 1616 and as a consequence was severely handicapped physically as well as mentally, his wife Anna ruled the Duchy of Prussia in his name until John Sigismund died of a second stroke in 1619, aged 47. From 1619 to 1640, George William was elector of Brandenburg and duke of Prussia.