Is it possible for my family to immigrate based on family relationship?

If you are a U.S. citizen or a permanent resident, your close family members can immigrate based on their relationship to you. Depending on whether you are a U.S. citizen or a permanent resident, and the type of your relationship with the family members, applicants fall into different categories, and may have to wait a number of years before they can immigrate. 

Immediate relatives: This category includes; spouses, parents and unmarried children (under the age of 21) of U.S. citizens only. There is no waiting period for immediate relatives, and processing for these visas will be relatively quick.

First Family Preference: This category includes unmarried adult (over the age of 21) children of U.S. citizens. The waiting period for this category can be between six and seven years.

Second Family Preference: is divided into two subgroups, 2a and 2b. 

The 2a category is reserved for spouses and unmarried children under 21 of U. S. permanent residents. The waiting period is between four and five years 

The 2b category includes unmarried children of any age of U. S. permanent residents. The waiting period for this category is currently between seven and eight years.

Third Family Preference: This category is meant for married children of U.S. citizens and the waiting time is about nine to ten years. 

Fourth Family Preference: This category is reserved for brothers and sisters of U.S. citizens and the waiting period for visas in this category is thirteen to fourteen years.