Is it permissible for two individuals who helped an expatriate in his court case to take a percentage of the financial amount awarded to the expatriate, whether the expatriate knows about it or not?

They are not permitted to take anything from the victim's right (due to him) without his permission and consent. If he is mentally incapacitated, then the consent of his guardian is necessary. His guardian is not permitted to donate any of his money. If they are entitled to something by agreement or custom, then they should take it through lawful means. However, taking his money without the knowledge and consent of whoever's consent is considered valid is impermissible.