Six months later, the death of his cousin John Augustus, Prince of Anhalt-Zerbst, without any issue made him and his older and only surviving brother, John Louis II, the heirs of Anhalt-Zerbst as co-rulers. Christian August remained in Stettin and his brother took full charge of the government, but he died only four years later, unmarried and childless. For this reason, Christian August had to leave Stettin and return to Zerbst, but he only reigned four months until his own death.