He was the oldest surviving son of Johann Ernst, Duke of Saxe-Coburg-Saalfeld and his first wife, Sophie Hedwig of Saxe-Merseburg.

His father, the duke Johann Ernst, determined the common government of the brothers with indivisibility of the duchy upon his death, in 1729.

Christian Ernst made his residence in Saalfeld and Franz Josias moved into the Veste Coburg.

The double government soon proved impossible, and this forced the settlement of the "Coburg Eisenberg Roemhilder of Hereditary Controversy", whereby Christian Ernst received Coburg, Rodach, Mönchröden and half Neuhaus.

Christian Ernst died childless and all his inheritance was taken by his half-brother, Franz Josias.