The law should have nothing to do with the will and inheritance of someone. It should be the decision of the father or the parents to decide whether they would want their child to have whatever they have after they are no more or not if they think he is living a dishonorable and disgraceful life, they decide to take and no court or law should force them to not do it if their child is dishonorable or whatever, it's their child, so just let them decide what to do with the inheritance.
If that's what he thinks that the law can alter the decision of the owner of the inheritance, he's just going waste his resources paying for the legal counsel.
What he needs to do is just to be kind to his parents and ask politely so that he might given even a bit of it.
Parents want the best for us and they're not going to like to see us suffer. So, this could be just a test for him.