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). If you're planning to petition a family member for a green card, you'll most likely need to prepare Form I864, Affidavit of Support.Typically, in order to claim US domicile, the Affidavit of Support sponsor must be residing in the United States. Download a proof of residency letter template for family members, notarized or non-notarized, tailored for legal use. MV-16 Affidavit to Certify Immediate Family Relationship (PDF, 51.09 KB) Department of Revenue How can we help? This guide will explain how to prove domicile when filling out Form I-864 ("Affidavit of Support").