If you want to become a lawful permanent resident based on the fact that you have a relative who is a citizen of the United States or is a lawful permanent resident, your relative in the U.S. will need to sponsor you and prove he/she has enough income or assets to support you, the intending immigrant(s) when in the United States. The priorities and preferences of who can qualify are below:

Immediate Relatives of U.S Citizens (IR)
These types of immigrant visas are based on a close family relationship with a U.S. citizen, including spouses, children, and parents. Additionally, a U.S. citizen can sponsor a child adopted or to be adopted from abroad. The Immediate Relative (IR-1) classification includes:

Spouse of a U.S. Citizen (IR-1)
Unmarried Child Under 21 Years of Age of a U.S. Citizen (IR-2)
Orphan adopted abroad by a U.S. Citizen (IR-3)
Orphan to be adopted in the United States by a U.S. Citizen (IR-4)
Parent of a U.S. Citizen who is at least 21 years old (IR-5)
Limited Family-Based Immigrants
These types of immigrant classifications involve specific, more distant, family relationships with a U.S. citizen and some specified relationships with a Lawful Permanent Resident. Under immigration law, there are fiscal year numerical limitations on family preference immigrants.

Family First Preference (F1): Unmarried sons and daughters of U.S. citizens, and their children, if any (23,400 per year).
Family Second Preference (F2): Spouses, minor children, and unmarried sons and daughters (over age 20) of lawful permanent residents (114,200 per year).
Family Third Preference (F3): Married sons and daughters of U.S. citizens, and their spouses and children (23,400 per year).
Family Fourth Preference (F4): Brothers and sisters of United States citizens, and their spouses and children, provided the U.S. citizens are at least 21 years of age (65,000 per year).