Permanent immigration in the U.S. comes with a variety of rights and privileges. One method to obtaining lawful permanent residency is through a relative who is either a citizen of the U.S. or a lawful permanent resident.

Steps

There are two categories for unlimited family-based immigration:

Immediate Relatives of U.S. Citizens (IR): A spouse, widow or unmarried child under the age or 21 of a U.S. citizen. This category also includes parents of adult U.S. citizens
Returning Residents (SB): Immigrants who previously lived in the U.S. under lawful permanent resident status. These individuals should be returning to live in the U.S. after being abroad for more than one year.
There are four preference categories for limited family-based immigration:

First Preference: Unmarried children over the age of 21 of U.S. citizens.
Second Preference: Spouses of lawful permanent residents, their unmarried children under the age of 21, and unmarried children under the age of 21 of lawful permanent residents.
Third Preference: Married children of U.S. citizens.
Fourth Preference: Siblings of adult U.S. citizens.
Your relative should first submit an immigrant visa petition, I-130 Petition for Alien Relative. This form should be accompanied by proof of your relationship to your relative.

Upon approval of this petition, the Department of State will determine if an immigrant visa number is available for you. When a number becomes available, you may apply for assignment of that number.

In order to sponsor a relative for lawful permanent residency, you must prove the following:

You are a citizen or a lawful permanent resident of the U.S.
You can support your relative at 125% above the mandated poverty line.
You must also show proof of your relationship with your relative.