In 1669 John Charles bought the Fürstenhof ("Princely court") of Gelnhausen, which included the Residenz, gardens and parcels of land that had first been granted by the Holy Roman Emperor to an earlier Wittelsbach, the Elector Palatine Louis III in 1435.

[1] Although Sophie Amalie died 30 November 1695 without having borne him a male heir, John Charles wrote Christian on 25 July 1696 declaring that if, feeling unable to continue living alone and heeding his heart's desire, he were to remarry it would only be a marriage of affection, since he was in no position to maintain a lady of rank.

[1][2] Within weeks John Charles found himself trying to conciliate his disapproving brother, disclosing the marriage but assuring him that it was a strictly private arrangement, and that should any children be born thereof he "would claim no more for them than to be taken as nobles, so that there is nothing to fear with regard to the succession.

He petitioned the Emperor to make his wife an Imperial countess, while Christian II refused to recognise the children born to his brother's marriage subsequently (three sons and two daughters) as agnates of the dynasty.

In the Wittelsbach family compact of 1771 establishing reciprocal inheritance rights between the Palatine and Bavarian branches, heirs to their realms were restricted to agnates who were legitimate and "not born of unequal marriage" (nicht ex dispari matrimonio).

[2] However the Peace of Teschen which concluded the War of the Bavarian Succession in 1779 finally recognised, in Article 8, the dynastic rights of the descendants of John Charles and Esther Marie von Witzleben, whose grandson, Wilhelm (1752-1837), received in 1803 the Duchy of Berg as an appanage from the Elector of Bavaria in compensation for the cession of his territories on the left bank of the Rhine to Napoleon.