Simplify the following text for a Grade 6 native English-speaking person.
Original: Approval for the marriage was granted by the Dutch parliament ( necessary by law for the Prince of Orange to remain heir to the throne ) , but MÃ xima 's father offered not to attend the wedding .
Simplified: This is necessary by law for the Prince of Orange to be able to become king . Because of the research around his involvement in the Dirty War , MÃ xima 's father offered not to attend the wedding .