Can my boyfriend adopt my son if the biological father never sign the bith certificate and has never been in my sons life?

I don't know, but may I recommend you wait until you are married.

The answer is "maybe".

Even if his bio father has never been involved in the child's life--he still has rights.

Get a lawyer specializing in adoption law in your area. They'll walk you through the steps you need to take for an adoption to take place.

And--you may have to be married first. Many areas require a legal commitment before allowing an adoption to take place.

First it may depend on the state, some states will still require you to be married, the boyfriend does not count in some area. And they do require often that the relationship be at least one year old.

Next the bio father will have to be contacted, he will have to sign over his rights, and/or if he does not resond, the court and order the rights taken away. He may not be using any rights, but he has always had the right to sue in court for paternity, so an adoptoin takes his right to file for paternity away,