There are many rules surrounding how to get a green card for a family member. They are put into different categories depending on their connection to the United States and relationship thereof. In order to be considered an immediate relative, you must be related to a U.S. citizen and either be their spouse, child under the age of 21, or parent (provided that the citizen is over the age of 21). Others are considered to be preference relatives, which includes siblings, unmarried children over the age of 21, and any relatives of immigrants that already have already been granted permanent residency in the US.
If you are not an immediate family member, you may be required to wait for a visa number after your relative files a petition for your green card. The National Visa Center makes these numbers available for applicants. Depending on the time of the year and your specific qualifications, you may not immediately be given one of these. Additionally, there may be other limitations that apply depending on your country of origin.
Family green card and immigration attorney Juan C. Perez can help guide you through the right application so you can maximize your chances of gaining permanent US residency.