Form I-601 is used to request a waiver of certain grounds of inadmissibility. For the Party-membership waiver under INA section 212(a)(3)(D)(iv), the applicant must be the parent, spouse, son, daughter, brother, or sister of a U.S. citizen, or the spouse, son, or daughter of a lawful permanent resident. USCIS may grant the waiver on humanitarian grounds, to keep a family together, or where approval otherwise serves the public interest, so long as the applicant is not a threat to U.S. security. Having a qualifying relative establishes only part of the eligibility analysis.