Original: John Casimir (d 1633 heirless), the older son of John Frederick II, and John Ernest (d 1638 heirless), the younger son of John Frederick II, received together the territory of Saxe-Coburg-Eisenach, but got a legal guardian because they were underage.
Simplified: John Casimir took Saxe-Weimar The older son of John Frederick II, and John Ernest (d 1638 heirless), the younger son of John Frederick II, received together the territory of Saxe-Coburg-Eisenach.