Custody for the father in Egypt

My nephew was born in United States and has the American passport and his dad is Egyptian with American passport and his mother is Egyptian. They got divorced when the child was 9 month and left the in United States and she went to Egypt to her mother. We tried to get her back but she didn’t want to said it doesn’t matter my child doesn’t know me. 4 years went by, she got to see her son pictures every 2 weeks and visited him this year when we went to vacation to Egypt. While we were entering the airport she was waiting for us and she took the child and started screaming and police in airport came and took us and they said Egypt rules for the mother take the child with her. We kept explained the child doesn’t know her and has his own life, etc.
my question is can my brother do anything about to regain the custody back?
1.What age can he take the child back?
2. Is there law where a child can visit his dad out of state and come back to Egypt again?
3. What document do we need to prove she may not be good fit for the child ?
4. If the child goes to school in Egypt, can his dad check his document and talk to school about his child or he needs her permission first?
5. For visitation, if the father can’t come to Egypt can his aunt and grandmother visit him instead?
6. Can the child travel with us inside of Egypt since she put a restriction on traveling.