My son is 18 months old. He has never met his bio father and I don't want him to. Nobodys name is listed as father on his because. How does my fiancé go about adopting him?

So you actually DO know who the father is, and just don't want your son to know? He's going to have to know eventually, you know-if only for medical background. If he finds out from someone besides you, it's going to be VERY bad.

Either way, for a step parent adoption to happen:

1. Get married. Most states require that you be married for some period before an adoption can happen.
2. Get a lawyer.
3. Get the biological father to agree to sign away his rights. Let me be VERY clear here: If you know who the biological father is and you lie about it, he CAN come back and overturn an adoption later.
4. If he will not agree, and you cannot PROVE that he is a danger to your child--you are out of luck. Your best option at that point is to go for child support--which, by the way, you should already be getting. It's not for YOU, it's for the child, and even if you don't need it, it can be put away toward a college fund.
5. If he DOES agree, you all go to court for him to relinquish his rights and for your husband to adopt.