Parents living abroad; guardian in US

No, if he has parents who are legally responsible for him (not a court ordered change of guardianship), it is their financial information that will be used on his FA applications, FAFSA and CSS. If he has a US address, he can use that, but the parents still fill out the forms.

If his parents have little money, that usually works out in his favor. He may get more need based aid than if you file using your financials.