Nine year olds are old enough to comprehend pretty serious stuff. He wants to run away because he’s afraid and unsure of how to cope with such a scary situation, but pacifying him is not the way to go. His parents should sit down with him and explain that they will both be there to talk to him about anything that he needs to talk about, and you should offer to do the same. He should hear that things are going to be different, but that doesn’t mean that things will be bad. He needs to be reminded that he is the most important person in this situation, and everyone will be looking out for his best interest. It’s okay to be scared and upset, and it is okay to cry.. but running away won’t solve anything. It also won’t change his parents’ decision, which may be the outcome he is hoping for, and acting out of desperation.