U.S. Family-Based Immigration Policy. Congressional Research Service, Library of Congress. William A. Kandel. February 17, 2016.
Family reunification is a key principle underlying U.S. immigration policy. It is embodied in the Immigration and Nationality Act (INA), which specifies numerical limits for five family-based admission categories, as well as a per-country limit on total family-based admissions. The five categories include immediate relatives of U.S. citizens and four other family-based categories that vary according to individual characteristics such as the legal status of the petitioning U.S.-based relative, and the age, family relationship, and marital status of the prospective immigrant.
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