How long will it take when filing for a sibling

Depending on the country... it is now between 12-25 years.

You can check the DOS visa bulletin. Look for family based preferences, the categrory for brother or sister of an adult US citizen is FB-4. if their country of birth is not listed, it will be in the first column, "all other chargeability areas" . This is updated every month. Visa Bulletin March 2009 (http://travel.state.gov/visa/frvi/bulletin/bulletin_4428.html)

Please note that filing the I-130 relative petition will create the priority date (place in line), but will also show a possible intent to immigrate, which could affect NIV applications. Discuss with an experienced immigration attorney if the sibling is intending to enter the US prior to the current backlog. Good luck!