Name Change, Foreign Father

My question involves name change laws in the State of:Missouri
My Step daughter is from another country. My wife is becoming a U.S. citizen now and we want to change her daughter's name to my last name before submitting forms for her citizenship. The father's whereabouts are unknown and he is not on the birth cert. He also denies that he is the father and has had no contact since before birth. What are our steps to the change?

How old is your step-daughter?

Generally, you need to have the consent of both parents before the child's name can be changed. Since you're unable to locate her father, you'll likely have to publish notifications in several newspapers.

You can look at the basic form here, but you'd do well to consult an attorney before you get started.