You are in category F2. As with all categories, it depends on how many people apply and their priority date. Do check the USCIS web site periodically to see you current country status.
You can get an idea of how long it will take by keeping up with the State Department's visa bulletin -- http://travel.state.gov/visa/bulletin/bulletin_1360.html. As my colleague noted, you're currently in the F2A category. Next month, they will be processing applications in that category that were filed in October 2010. There is a new visa bulletin every month, and though it often progresses regularly, there's no guarantee -- some months it won't move or it'll go backward. If your father is eligible to become a citizen, that will make your process go faster.
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I agree with Laura. Check the priority date for F2A which is your category and then go to country of chargeability - India. It will take 3 years approx. if you go with the current dates. This is just an approximation, no one can really predict how many numbers are used each year. Also, you qualify in this category based on your unmarried status. If by the time the date is current, you father seeks naturalization, then your petition can be upgraded to USC son/ daughter, and you can go with those numbers.
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However long it takes for the priority date to become current. The movement of priority dates cannot be predicted.
For the latest visa bulletin see http://www.engnishimura.com/priority-dates/current
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.