Simplify the following text for a Grade 6 native English-speaking person.
Original: They were descendants of Charles of Valois , the fourth son of King Philip III and based their claim to be ahead of Edward III of England and Joan II of Navarre according to the Salic law .
Simplified: The kings of the House of Valois were descended from Charles of Valois who was the third son of Philip III of France . They claimed the Salic law put them ahead of Edward III of England to rule France .