Which realm was passed onto this duke whose father passed away before his birth and whose history was documented in the memoirs of Helene Kottanner?
Helene Kottanner:  She is primarily known to history as the author of memoirs about the years 1439 and 1440, when king Albert II of Germany died and his son Ladislaus the Posthumous was born. Ladislaus the Posthumous:  He was the posthumous son of Albert of Habsburg and Elizabeth of Luxembourg. Ladislaus the Posthumous:  Albert had bequeathed all his realms to his future son on his deathbed, but only the Estates of Austria accepted his last will.
Estates of Austria