Poor kid. Are the parents moving away from where they are right now and the boy will lose his school and his friends as he’s known them?
I’d just try and talk to him about how he will need to talk to his parents more than before about what he needs, what’s important to him, what he wants and why he wants it. I’d ask him to be patient because his parents are going to show a side of hurt in themselves they might normally keep to themselves, that they might not be right or wrong but it will be hard to watch. Remind him he’s still loved even in disorder.
If you are friends with the parents then I hope you can as politely as possible suggest they be as amicable and affording to their kid as they can. Not in the giving in way at all though. It takes a bigger person to put their kids a close second to their own need of divorce than to throw in to selfishness and get as far away at any cost as possible to “start over”.