How long does it take for a sibling to petition for another sibling?

A U.S. citizen may apply for a sibling in the Family-Based Fourth Preference (F4) visa category. Unfortunately, there is a very long backlog for visas in that category - according to the March, 2016 Visa Bulletin issued by the U.S. Department of State, visas are now available for final action for those with Priority Dates (original filing dates) of July, 2003 or earlier. While that may appear to be a backlog of about 13 years, often less than a year's worth of backlog is cleared each year in this category, and so for a newly filed case the wait may be 20 years or even longer. The filing of an application in the F4 category would NOT permit the foreign national to remain in the U.S. while waiting for the visa category to "become current." For this reason F4 is rarely a satisfactory immigration strategy, and it may be worthwhile for your brother to consult with an immigration attorney to explore whether there may be some employment-based or other strategies available to meet his goals.