After John III's death on 11 June 1420, the two principalities were reunited under Frederick VI, who had become Elector Frederick I of Brandenburg in 1415. Upon Frederick I's death on 21 September 1440, his territories were divided between his sons; John received the principality of Bayreuth (Brandenburg-Kulmbach), Frederick received Brandenburg, and Albert received Ansbach.
Frederick (Middle High German: Friderich, Standard German: Friedrich; 21 September 1371 – 20 September 1440) was the last Burgrave of Nuremberg from 1397 to 1427 (as Frederick VI), Margrave of Brandenburg-Ansbach from 1398, Margrave of Brandenburg-Kulmbach from 1420, and Elector of Brandenburg (as Frederick I) from 1415 until his death.
15. Frederick I, Margrave of Meissen, 1257–1323 16. Frederick II, Margrave of Meissen, 1310–1349 17. Frederick III, Landgrave of Thuringia, 1332–1381 18. Frederick I, Elector of Saxony, 1370–1428 19. Frederick II, Elector of Saxony, 1412–1464 20. Ernest, Elector of Saxony, 1441–1486 21. John, Elector of Saxony, 1468–1532 22.
John Frederick, Margrave of Brandenburg-Ansbach (father of 187) 375. Princess Eleonore Erdmuthe of Saxe-Eisenach (mother of 187) 376. William Henry, Prince of Nassau-Usingen (father of 188) 377. Charlotte Amalie, Countess of Nassau-Dillenburg (mother of 188) 378. John William III, Duke of Saxe-Eisenach (father of 189) 379.