U.S. immigration law recognizes two tracks for family sponsorship. Immediate relatives of U.S. citizens — spouses, unmarried children under 21, and parents (where the citizen is 21 or older) — face no annual numerical limit. Everyone else falls under the family preference system, which is subject to annual caps and visa-bulletin waiting periods: F1 (unmarried adult children of citizens), F2A (spouses and children of permanent residents), F2B (unmarried adult children of permanent residents), F3 (married children of citizens), and F4 (siblings of citizens).
The process generally starts with a petition establishing the relationship, followed by either adjustment of status (if the beneficiary is in the U.S.) or consular processing (if abroad) once a visa number is available.