Simplify the following text for a Grade 10 native English-speaking person.
Original: At the time of his birth , Charles Emmanuel was not the heir to the Duchy of Savoy ; his older brother Prince Victor Amadeus John Philip , Prince of Piedmont , was the heir apparent .
Simplified: At the time of his birth , Charles Emmanuel was styled the Duke of Aosta as his older brother Victor Amadeus , Prince of Piedmont was the Heir apparent .