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. Completing and signing Form I-864 makes you the sponsor.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). Each joint sponsor must fill out a separate I864 form. In their form, they will include the names of all immigrants that they will personally be sponsoring. This video is dedicated to the form I-864A, the contract between sponsor and household member.