Much confusion surrounds the need to submit I751 affidavits and how to write them. We explain and provide an I-751 affidavit sample.1. Talk to the person immigrating to the US. The person for whom you write an affidavit should be someone you know very well. An I130 affidavit is a written statement from friends, family members, or associates who can attest to the genuine nature of your marriage. By signing Form I-864, you are agreeing to use your resources to support the intending immigrants named in this affidavit, if it becomes necessary. An affidavit or letter can be used to fill gaps, corroborate or support other evidence or explain shortcomings or weaknesses in a petition.