He was the eldest son of Philipp Wolfgang of Fleckenstein-Dagstuhl (d. 1618) and his first wife, Anna Alexandria of Rappoltstein (7 March 1565 – 9 April 1610).

Georg II gained considerable power as guardian and regent of the still underage Count Friedrich Casimir and the counties of Hanau-Lichtenberg and Hanau-Münzenberg during the final phases of the Thirty Years' War.

The Lordship of Fleckenstein came to feel the full force of the Thirty Years' War in 1622, when commander Ernst von Mansfeld spent the winter in the Upper Rhine area.

In Strasbourg, Count Philipp Wolfgang of Hanau-Lichtenberg wrote his will, in which he made his son Friedrich Casimir his sole hier and successor, based on the primogeniture decree, which was in force in the ruling family of Hanau since 1375.

In case Friedrich Casimir was still underage when he inherited the county, his regents would be Georg II and Count Johann Ernst of Hanau-Münzenberg.

His ward, Count Friedrich Casimir, inherited Hanau-Münzenberg in a politically precarious situation: Georg II of Fleckenstein died on 31 January 1644 at Hanau, the last baron of the Fleckenstein-Dagstuhl line.