In 1616 he married Elisabeth Charlotte, sister of the Elector Palatine, and they became the parents of four children. In 1619 he succeeded his father to become Elector of Brandenburg.
He was both a pious Calvinist and a greedy gourmandizer. Even though he was a Protestant, he was strongly influenced by the Catholic Count Adam von Schwarzenberg, which contributed to the initial neutrality of Brandenburg in the early years of the Thirty Years' War.
However, his indecisive behaviour led to a spineless foreign policy and, as a result, his territories were severely devastated by the soldiers of both sides. According to his descendant, Frederick the
Great, he was "utterly unfit to rule".
As brother-in-law of the 'Winter King' of Bohemia, he opposed the Emperor while at the same time owing feudal loyalty to the same Emperor. However, as the Estates of his three properties--Brandenburg, East-Prussia and Cleves-Mark--controlled the finances and were
unwilling to supply money for warfare, he was unable to assist either side effectively.
In 1627 he attacked his other brother-in-law, King Gustavus Adolphus of Sweden, for using Prussia as a war-base against Poland, a short campaign ending in favour of the Swedish king. In June 1631 Gustavus Adolphus forced him to join the Protestant side, whether he liked it or not, and Count Schwarzenberg was made to resign.
However, in 1635 Schwarzenberg returned to office and, making peace with the Emperor, adhered to the Treaty of Prague. Both Georg Wilhelm and Schwarzenberg hoped to use the Emperor to break the power of the Estates and drive the Swedes out of Pommerania, which Georg Wilhelm was due to inherit. However, neither scheme succeeded. Furthermore his revenues fell even further and, in 1638, he moved his residence to Konigsbergen in East-Prussia, leaving the Electorate to
be administered by Count von Schwarzenberg. When he died of dropsy, he left a State and people exhausted and terrorized.
 

Source: Leo van de Pas