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). These additional financial sponsors also have to submit an Affidavit of Support, proof of their income, and proof of their legal status in the United States.For the typical sponsor who has always lived in the United States, no special evidence is required to prove domicile. Proof of U.S. domicile is required for the I864. Learn examples of proof of domicile along with proof of domicile documents required. This guide will clarify what domicile is, how to establish it, and the documentation you need for proof of domicile. Country of Domicile enter the joint sponsor's country of domicile (most sponsors will enter "US" as the country of their domicile). 6. If you are in the US on a student visa and your plans change, you may be able to change your immigration status and receive a green card. You could certainly list your joint account (with your grandfather) as well as your parents' foreign bank account as proof of the assets.