Family-Based Immigration for Relatives Green Cards
Petitioners must always be adults, 21 years of age or older. They may be either U.S. citizens (by birth or naturalization) or U.S. permanent residents (green card holders). The list of relatives for whom a permanent resident can file is not the same as the relatives for whom a U.S. citizen may file as sponsor or petitioner.
Both U.S. citizens and green card holders may petition for their spouses, minor children, and unmarried sons and daughters (21 or older). However, as mentioned before, there are other differences between the relatives who may be beneficiaries of a case filed by a U.S. citizen, as opposed to those in a case filed by a green card holder. U.S. citizens may petition for their parents, married sons and daughters, as well as their siblings. (U.S. citizens can also file for fiancé/es, but because this is a temporary category, it is not included in the chart pertaining to permanent immigration benefits.) http://www.greencardfamily.com/news/news2012/news2012_0615.htm
The question of how long a particular case will take can be a bit complicated. The United States sets strict annual limits on the number of individuals who may immigrate permanently each year. This is determined by the case category and country of chargeability.
The date that the petition for a relative (Form I-130) is filed establishes the priority date. This, essentially, sets the family member's place in the queue. The waiting time in some categories is measured in years and, in some situations, is more than a decade. The situation for those cases categorized as immediate relatives, as explained below, is far more favorable.
The U.S. Department of State (DOS) controls the annual legal limits on permanent immigration to the United States by the use of visa numbers, available in accordance with the legal limits. The availability of visa numbers by category is reflected in the monthly DOS visa bulletin.
Some relatives of U.S. citizens are categorized as immediate relatives. These cases are not subject to visa number backlog, and are not reflected in the visa bulletin. These cases can move forward without waiting times for visa numbers. The paperwork needs to be processed by the U.S. Citizenship and Immigration Services and, in some cases, the DOS, through a U.S. consulate abroad. The waiting time for this paperwork processing is usually far less than the waiting time for visa number availability in family-preference cases.