What documents do I needed to adopt my step-son?

You will need the consent of his birth father. His birth father will either have to willingly terminate his parental rights, or you will have to find grounds to have them terminated such as abandonment of the child. If you cannot locate the birth father, you must prove to the court that you have gone above and beyond in trying to find him, and then you will be able to publish a public notice in the paper stating your intention to adopt your stepson. Aside from the legal papers for filing for the adoption you will also need marriage certificates (both yours to your wife, and hers to the ex if they were married) divorce decree, custody/child support papers, and birth certificates for everyone in the house. If you call your local courthouse they can let you know what forms you will need for a stepparent adoption, each state is a little different when it comes to the actual court forms.