The F4 visa is restricted to brothers and sisters of U.S. citizens, and their spouses and children. The U.S. citizen must be at least 21 years old.
Other F visas include the F1, for any unmarried sons and daughters of U.S. citizens, and their children, if they have any. An F2 visa is for the spouses, minors and unmarried children of lawful permanent residents. An F3 visa covers the married sons and daughters of U.S. citizens, as well as their spouse and children.
As of February 2010, only 65,000 F4 visas are granted each year. If there are too many applicants, they are prioritized according to their filing dates.
The U.S. citizen or lawful permanent resident must have a residence in the U.S. before an F4 visa can be issued.
Applicants require approval by both the Department of Homeland Security and the Immigration Service before processing can begin at the National Visa Center.
