These relationships fall into various categories known as "preferences." These preferences are subject to annual quotas. Even if one can establish a relationship to a U.S. citizen or permanent resident, it may be years before an alien can gain permanent residence to the U.S.A. because of the backed-up quota system.
Once a month the Department of State provides details through the Bureau of Consular Affairs of those people who are qualified to obtain permanent residence because there is a green card available for them in the quota system.
It is also important to note that there is a limit tothe number of green cards that are allocated to each foreign country, and for that reason, certain countries may be backed up further than other countries in the same preference category.
FAMILY RELATIONSHIPS QUALIFYING FOR PERMANENT RESIDENCE
Unmarried sons/daughters of U.S. citizens--theseare children over the age of 21 years;
Spouses and unmarried sons/daughters of permanent residence aliens;
This second preference category is divided into:
A) Spouses or children of an alien lawfully admitted for permanent residence;
B) Sons/daughters over the age of 21 years of an alien lawfully admitted for permanent residence.
Married sons/daughters of U.S. citizens;
Brothers/sisters of U.S. citizens.
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