[2] He succeeded his brother Adolph John II as Count Palatine of Kleeburg in 1701, and his cousin Charles XII, King of Sweden, as Duke of Zweibrücken in 1718.

As the last male member of his branch of the House of Wittelsbach, his territories were inherited by Christian III, Count Palatine of Zweibrücken-Birkenfeld.

Gustav failed in his aspirations, and the grand-mastership was confirmed in 1701 by the pope to be hereditary in the House of Farnese and its successors (the Dukes of Castro).

The Farnese duke was later succeeded in the position by his nearest male kinsman, the future king Charles III of Spain.

Upon the death of his cousin King Charles XII, Gustav of Stegeborg then became one of the eligible candidates for legitimate succession to the thrones of Sweden and of the grand duchy of Finland.