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). This guide will explain how to prove domicile when filling out Form I-864 ("Affidavit of Support").Consular processing support without the high price tag. Typically, in order to claim US domicile, the Affidavit of Support sponsor must be residing in the United States. There are five stages for application submission. 1.