had died without heirs. Ernest would then be called Duke of Saxe-Gotha-Altenburg.

When Ernest died in 1675, he left his seven sons a significantly enlarged territory. The eldest, Frederick I at first ruled jointly with his brothers until in 1680 the duchy was divided. The area around Gotha and also Altenburg passed to Frederick I, who retained the title of a Duke of Saxe-Gotha-Altenburg.