I am a family-based new immigrant. I will send out my I-1485 application to USCIS very soon. I have a 20 years son who will be included in my I-1485 application. I am worry about that he may reach 21 years old before the  I-1485 approval. Could you please give me some idea about the "aging-out process"?

Answer:

If one of dependent child is about to reach 21 years of age and seeks immigrant status as the dependent beneficiary of either family-based or employment-based or for that matter, any other basis, it is the USCIS practice to take such case as the "top priority" case and expedite the process so that the green card applications for the entire family are adjudicated before the child reaches 21 years of age.

Consequently, not only the aging out child but also the parents and other siblings receive "expedite" processing and cases are approved in a fairly short period of time. This aging-out expedite process has been available in the USCIS.

Currently, aging-out expedite works well in the family-based proceedings. Such aging-out expedite works at the USCIS local district office one-step I-130/I-485 proceedings. The USCIS district offices approves I-485 applications for the entire family members in the event that a child will reach 21 years of age in a few months.

http://www.greencardfamily.com/question/question2014/Expedite-Aging-Out-Process_0218.htm