Whether your son can immigrate with you depends upon a number of factors, including your country of birth and application of the Child Status Protection Act. Pleas consult with an immigration attorney to discuss this case further.
Your son may be able to immigrate. We would need to see if under the CSPA he is considered a 'child' or not. Some of that calculation depends on how long it took the USCIS to adjudicate the I-130.
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Take the number of days the I-130 was pending - from the day filed to the day approved, and subtract from your son's age on August 1, 2013. If his "adjusted age" will land him under 21, and provided the priority stays current, he might.
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F2b for August 2013 is at December 1, 2005, so the visa is not yet available.
The above is intended only as general information, and does not constitute legal advice. You must speak with an attorney to discuss your individual case.
Looking at the Visa Bulletin, it isn't likely. It depends on whether he would be protected under CSPA at the time the date is current.
Dhenu Savla, Esq.
This answer does not create an attorney-client relationship and is not meant to be relied upon as legal advice.