For relatives not classified as immediate relatives, family-based immigration falls under the family preference categories: F1: Unmarried sons and daughters (21 or older) of U.S. citizens F2A: Spouses and unmarried children (under 21) of green card holders F2B: Unmarried sons and daughters (21 or older) of green card holders F3: Married sons and daughters of U.S. citizens F4: Brothers and sisters of U.S. citizens