Family-Based Preference Categories
The Immigration and Nationality Act provides that a limited number of immigrant visas may be issued to grant foreign nationals permanent residency in the U.S. every year based on close family relationships. The following individuals may file for family-based preference classification:
Family-based First Preference (F1): Unmarried sons and daughters of U.S. citizens. Note that “sons and daughters” are those grown children of U.S. citizens who no longer qualify as “immediate relatives” because they are either married or over the age of 21.
Family-based Second Preference (F2): Spouses and children, and unmarried sons and daughters, aged 21 or older, of permanent residents. Spouses and children of permanent residents are allocated a separate quota (“2A”) than unmarried sons and daughters (“2B”). Note that there is no preference classification for married sons and daughters of permanent residents. If the adult son or daughter of a permanent resident over age 21 gets married, he loses eligibility to become a permanent resident on the basis of the parent's I-130 filed on his behalf.
Family-based Third Preference (F3): Married sons and daughters of U.S. citizens.
Family-based Fourth Preference (F4): Brothers and sisters of adult U.S. citizens (over age 21).
All of the above-noted classifications are subject to numerical limits and therefore there is a backlog of visa availability, making the wait for an immigrant visa years or decades long in some cases. Allocation of visa numbers is projected in the Department of State's monthly Visa Bulletin.