Which of the following is NOT classified as an Immediate Relative immigrant?

In the context of U.S. immigration, Immediate Relative immigrants are defined specifically as certain close family members of U.S. citizens who qualify for a visa without being subject to annual caps. This category includes the spouse of a U.S. citizen, minor children (unmarried, under 21) of a U.S. citizen, and parents of a U.S. citizen who is at least 21 years old.

Siblings of a U.S. citizen, however, fall under a different classification and are not considered Immediate Relatives. Instead, they are classified as family preference immigrants, which means their visa availability is subject to annual limits and quotas, making the waiting time for them significantly longer compared to Immediate Relatives.

The distinction lies in the relationship's proximity to the U.S. citizen; Immediate Relatives are those who have the most direct familial ties, while siblings, despite being close relatives, do not meet the criteria for this category. Hence, the answer accurately reflects the immigration classification system.