
US Visa Singapore
F4 family visa is for brothers and sisters of adult US citizens. There is an annual quote of 65,000, plus any numbers not required by first three preferences (F1 - F3).
The US State Department maintain an updated monthly list of the wait times for family visa applications. The monthly list of wait times is called the "Visa Bulletin" and can be found on the US Department of State website. The Visa Bulletin will show various dates under each family visa category (F1 - F4). The date listed therein is the date in which the applications they are currently processing were filed.
Please note that once you apply for a F4 family visa that such applicant would not qualify for a tourist, business or student visa because such visas require an intent "not" to immigrate to the US. By filing the F4 family visa application you are declaring you have an intent to immigrate to the US and such makes you ineligible to receive a "temporary non-immigrant visa" such as tourist, business or students visas.
F4 family visas allow the holder to receive a US green card. However, the wait for F4 family visas to become available takes many years (10+). Thus, the F4 family visa is only an option for applicants who do not need to travel to the US in the near future.