Simplify the following text for a Grade 12 native English-speaking person.
Original: The last Muslim ruler of Granada , Muhammad XII , better known as King Boabdil , surrendered his kingdom to Isabella I of Castile , who with her husband Ferdinand II of Aragon were known as the Catholic Monarchs ( los Reyes CatÃ licos ) .
Simplified: The last Muslim ruler of Granada surrendered ( gave up ) his kingdom to Ferdinand II of Aragon and Isabella I of Castile , the Catholic kings ( los Reyes CatÃ licos ) .