Scope and purpose
Qualifying immediate relatives include specified spouses, children and parents of U.S. citizens, subject to statutory definitions. Other family relationships can fall within the preferences allocated under INA §203. Per-country rules are addressed separately in INA §202.
Related rules and practical context
Form I-130 establishes a qualifying relationship; adjustment under INA §245 still requires its own eligibility and admissibility analysis. A family petition does not erase a ground of inadmissibility.