Paternity for adoption

I want to know that if I were to try to adopt my wife's son from a previous marriage would the alleged father have to prove that he is the father of the child. My wife says that the man who's name is on the birth certificate as the father is not the biological father. Would I be able to get him to submit to a paternity test to prove he is the father? I reside in Utah and the child's alleged father in Idaho.

Unfortunately, you failed to list which state you're from, and the laws vary from state to state, so it's highly unlikely your post will draw much in the way of useful information.