Principality of Lüneburg
In 1648, when George William's elder brother, Christian Louis, Prince of Calenberg, inherited the Principality of Lüneburg from their paternal uncle, Frederick IV, he gave Calenberg to George William in appanage. Seventeen years later, in 1665, Christian Louis himself died childless, and George William inherited Luneburg as well. He then gave Calenberg to his next brother, John Frederick.