485, 14 years old, fingerprints?

My family filed 485 in the same time on July 2007. The PD is 05/30/2006, EB2.

We all received our green cards recently except my old son. He becomes 14 years old in the begining of December 2010.

 

He was asked for fingerprint two times recently.

1. Both he and I got a letter sending on 12/14/2010 for Code 1 fingerprints. The reason is Expired fingerprints.

We did fingerprint on 12/20/2010. I got my "Welcome" letter right after Chrismas.

2. A couple of days later, my son got the other letter for Code 3 fingerprints and biometrics. The letter was sent out on 12/22/2010. The reason becomes Initial Fingerprinting. He did that on 12/27/2010.

 

His case status online still shows Initial Review.

 

Can you advise what kind of reason makes his case delay? Thanks