1. The Fourth Preference for Brothers and Sisters of U.S. Citizens

The close family members of a U.S. citizen can qualify to immigrate to the United States, but they are subject to a numerical limit of immigrant visas available to them each year. Generally, the higher the preference, the quicker the alien will be eligible to receive a Green Card. The relatives in categories must wait for a visa to become available according to the following preferences:

• First preference: Unmarried Children over 21 year of age of U.S. Citizens (23,400 per year, plus unused visas from the Fourth Preference);

• Second Preference: Spouses and unmarried children (regardless of age) of U.S. permanent residents (114,000 per year, plus unused visas from the First Preference);

• Third Preference: Married sons and daughters of U.S. citizens, including their spouses and their minor children. (23,400 per year, plus unused visas from the First and Second Preferences);

• Fourth Preference: Brothers and sisters of U.S. citizens, including their spouses and their minor children. (65,000 per year, plus unused visas from the First, Second, and Third Preferences).

If an applicant does not qualify as an immediate relative, they may apply under one of the four preferences above. Since numerical caps apply to these categories, visa petitions are ranked chronologically based on a "first come, first serve basis." Also, because of the numerical cap, there are long waiting periods to obtain a visa in most of the family-based immigrant categories.

2. The Green Card Application for U.S. Citizen's Brothers and Sisters 

Family-sponsored immigration has an overall quota of about half million per year, plus unused numbers from employment-based preferences. Each preference is given a numerical quota per year to limit the number of immigrants admitted into the United States.

People who want to become immigrants are divided into categories based on a preference system. The immediate relatives of U.S. citizens, which includes parents, spouses and unmarried children under the age of 21, do not have to wait for an immigrant visa number to become available once the application filed for them is approved by the USCIS. 

To apply for a Green Card for a U.S. citizen's brother or sister, a U.S. citizen must be 21 years of age. Also, to qualify as a brother or sister of a U.S. citizen, both the brother or sister and the U.S. citizen must have been children of the same parent.

Immediate family members of the brother or sister may also apply for a Green Card with the brother or sister of a U.S. citizen at the same time. The annual visa allotment available for this preference is 65,000, plus any visas not used by the first three preferences. 

3. The Sibling Relationship for Immigration Petition

As a U.S. citizen, you can petition for:

1) brother or sister, and you have the same mother;

2) brother or sister, and you have the same father BUT different mothers;

3) brother or sister, you are related through your father, and one of you was born out of wedlock and legitimated;

4) brother or sister, you are related through your father, and one of you was born out of wedlock but not legitimated;

5) stepbrother or stepsister, and you now share a common parent;

6) stepbrother or stepsister, you now share a common parent, and one of you was born out of wedlock;

7) stepbrother or stepsister, you are related through your father, and one of you was born out of wedlock but not legitimated.

If either you or your sibling were born out of wedlock (your birth parents were not married when you were born), you must provide evidence that you took the actions necessary to satisfy the legitimation law of the birth country of the person born out of wedlock while the individual was under 18 years of age and unmarried. Legitimation laws require fathers to legally acknowledge their children.