There are several different types of relationship which allow you to obtain a green card through family members. If you are an immediate relative of a U.S. citizen, that person may be able to file a petition to bring you to the United States or to help you attain legal status if you are already living in the United States. Immediate relatives include spouses, unmarried children under the age of 21, and parents of U.S. citizen petitioners aged 21 or older.
There are also several preference categories under which you can qualify, including unmarried sons or daughters over the age of 21, married children of any age, and brothers and sisters of U.S. citizen petitioners 21 or older. Legal Permanent Residents of the United States can also file petitions for their family members, including spouses and unmarried children.