Simplify the following text for a Grade 7 native English-speaking person.
Original: Poseidon has broken an oath taken with Hades and Zeus to refrain from having any more children with mortal women as the children can become too powerful and become a threat .
Simplified: After World War II , Poseidon , Hades and Zeus had made an oath ( promise ) not to have any more children because they were too powerful . However , Poseidon had broken the oath .