If you are either a native-born or a naturalized U.S. citizen, and you have relatives who were born in another country, you may, in certain cases, be able to help them obtain U.S. lawful permanent residence (a green card).
If you started out with a green card and then became a naturalized U.S. citizen, you probably noticed that your rights to help family members immigrate were then quite limited. A green card holder can sponsor (file an I-130 petition for) only his or her spouse and unmarried children; but no one else. In fact, you may have filed petitions for these family members long ago, and still be waiting for them to immigrate.
Spouses and unmarried children of permanent residents, as well as various other family members, are called "preference relatives." That means that Congress set annual limits on the number of visas (green cards) available to them. Because the demand for these visas always exceeds the supply, preference relatives end up on waiting lists that last many years before they can immigrate to the United States.
But now that you're a citizen, the situation improves for:
Also note that same-sex marriages currently count for immigration law purposes, so long as they are recognized by the government of the state or country where they took place.
As a citizen, your spouse and your unmarried minor children (younger than age 21) are "immediate relatives." That means they can apply for lawful permanent residence right away, with no annual limits and no waiting lists to delay their progress.
You can either start the immigration process for them now by filing an initial I-130 petition for them with U.S. Citizenship and Immigration Services (USCIS) or, if you already started it while you were a green card holder, have them continue the process at a faster pace, by advising the relevant U.S. government office that you have become a citizen.
Unfortunately, even immediate relatives must go through a lot of application paperwork before they can get their green cards. The process often takes a year or more to complete. You can't avoid the paperwork. But at least you'll know that their cases are progressing as fast as possible.
If you have unmarried children who are already older than 21 (in visa preference category "2B"), and you've filed a petition for them, your U.S. citizenship turns them into what are called "first preference relatives." This is not as beneficial as being an immediate relative. It means that they are subject to annual limits on the number of visas and will have to wait for an available one before they can continue with their immigration process. However, they are fairly high on the priority list, and so will likely wait less time than people in other preference categories.
If you've already filed a petition to start the immigration process for your spouse or children (on USCIS Form I-130), but they're still on the waiting list for a visa or green card, you don't have to restart the process from the beginning. Instead, you can advance them forward. In other words, you don't have to file a new petition, and they don't have to lose their place in line. If they have become immediate relatives, they can jump straight to the head of the line and continue with the final stages of their applications for green cards.
If your children are older than 21, and you filed a petition for them already, they can go from the 2B waiting list to the first preference waiting list, with full credit for the years they have already waited. (In technical terms, they can use the same "priority date" as they had before.) In either case, the usual procedure is to send a copy of your citizenship certificate and a letter explaining the situation to whichever office is currently handling your family members' applications.
A further benefit to your U.S. citizenship is that as soon as your children become lawful permanent residents, they may also become instant citizens, so long as they're younger than age 18 when you become a citizen and they're living in the United States in your legal and physical custody.
Becoming a citizen allows you to start the immigration process for certain family members other than your spouse and unmarried children. These include your parents, married children, and brothers and sisters.
(It doesn't, however, include family members such as grandparents, aunts, uncles, cousins, nieces, and nephews.)
Not all of your eligible family members will become immediate relatives, however. Some of them will become preference relatives, and therefore have to wait many years before having the opportunity to immigrate through you.
Your parents benefit the most from your U.S. citizenship. They are considered your immediate relatives and can apply to immigrate to the United States right away, or as soon as you become age 21 or older. (As described earlier, however, even immediate relatives must get through the paperwork of immigrating, which tends to take around a year to complete.)
Your married children as well as your brothers and sisters benefit from your U.S. citizenship, because you can file I-130 petitions starting the immigration process for them. However, they will be considered your preference relatives, meaning that your petition won't get them a visa or green card anytime soon. First, they'll be put on a waiting list and subject to an annual limit on the number of visas that are given out.
Your married children will fall into the third preference category; your brothers and sisters into the fourth preference category. Both are fairly low on the priority list and are likely to wait many years (or even decades, in the case of siblings) before becoming eligible to immigrate to the United States.
To learn more about the process, talk to a local immigration attorney and check out How to Get a Foreign Family Member Into the U.S.