Can my brother be a joint sponsor if my spouse doesn’t meet criteria for affidavit of support?

In a marriage-based adjustment of status application, generally if the U.S. citizen spouse does not have sufficient documentable income to meet the Affidavit of Support requirements then it is necessary to have a joint sponsor, and that joint sponsor may be any U.S. citizen or Permanent Resident (including the brother of the beneficiary) who has sufficient documentable income and who is willing to assume the obligations contemplated in the Affidavit of Support. Both Affidavits of Support should be filed as supporting documents with the Adjustment of Status application. This is just one of the issues that can be significantly more complex than it appears just from reading the immigration forms, the USCIS website and the immigration regulations. It would be wise for you and your spouse to consult with an immigration attorney who, after learning all of the relevant information, could advise about eligibilities, options and strategies to attain your goals, and who then could offer legal representation in the often complex application process.