Family-based immigrant visas, also known as "green cards," allow U.S. citizens and lawful permanent residents (LPRs) to sponsor certain family members for immigration to the United States. In some cases, a U.S. citizen or LPR may want to sponsor their brother or sister for an immigrant visa.

To sponsor a sibling for an immigrant visa, the sponsoring U.S. citizen or LPR must meet certain eligibility requirements and submit a visa petition to U.S. Citizenship and Immigration Services (USCIS). The sibling must also meet certain eligibility requirements, including being a sibling of the sponsoring U.S. citizen or LPR and being the beneficiary of an approved immigrant visa petition.

One of the requirements for sponsoring a sibling for an immigrant visa is that the sponsor must provide a financial guarantee that they will support the sibling financially once they immigrate to the United States. This financial guarantee is often referred to as an "affidavit of support" or a "sponsorship agreement."

The affidavit of support is a legal contract in which the sponsoring U.S. citizen or LPR agrees to provide financial support to their sibling until the sibling becomes a U.S. citizen, dies, or is credited with 40 quarters of work (approximately 10 years of work). The affidavit of support is intended to ensure that the sponsored sibling does not become a public charge and relies on public benefits.

To meet the financial requirements of the affidavit of support, the sponsoring U.S. citizen or LPR must demonstrate that their income is at least 125% of the federal poverty level for their household size. If the sponsor's income is not sufficient, they may be required to obtain a joint sponsor who can also provide a financial guarantee.

Once the affidavit of support is completed and signed, it must be submitted to the National Visa Center (NVC) as part of the immigrant visa application process. The NVC will review the affidavit of support and may request additional information or documentation if necessary.

It's important to note that the affidavit of support is a legally binding agreement, and the sponsor can be held financially responsible if the sponsored sibling receives public benefits. Additionally, the affidavit of support remains in effect until it is terminated by the sponsor, the sponsored sibling becomes a U.S. citizen, or the sponsored sibling is credited with 40 quarters of work.

In conclusion, sponsoring a brother or sister for an immigrant visa requires a financial guarantee in the form of an affidavit of support. This legal agreement ensures that the sponsored sibling will not become a public charge and relies on public benefits. The sponsoring U.S. citizen or LPR must meet certain income requirements and may need to obtain a joint sponsor if their income is not sufficient.