This guide will clarify what domicile is, how to establish it, and the documentation you need for proof of domicile. If you want to sponsor someone for a family-based green card, you need to provide proof of a U.S. domicile in your Affidavit of Support (Form I-864).Proof of Domicile: The sponsor should be living in the United States or its territories. Typically, in order to claim US domicile, the Affidavit of Support sponsor must be residing in the United States.