If you have a joint sponsor, they must also complete Form I864. Step 4: Complete Affidavit of Support The person who signs the Affidavit of Support is also called the "sponsor.In today's video we are going to be filling out form i 864 the affidavit of support form for the joint sponsor. A fully completed and signed Affidavit of Support (Form I864) from the sponsor. In order to act as a sponsor, an individual must file a Form I-864, Affidavit of Support. Situations Where Sponsor is not Required. When applying for a green card through family sponsorship, one of the essential steps is completing the Affidavit of Support (Form I864). Some sponsors temporarily reside abroad and intend to move to the US once a family member's immigrant visa is issued. INA §§ 213A(a)(1), (d). When applying for a green card through family sponsorship, one of the essential steps is completing the Affidavit of Support (Form I864).