Simplify the following text for a Grade 10 native English-speaking person.
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: 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 .