I am getting married soon and my wife to be's 14 year old daughter wants me to adopt her. The father is in prison and has had very little contact over the past 12 years. Do we need his signiture or consent to go forward with the adoption?

Yes. Unless his rights have previously been terminated, he has to consent or have his rights involuntarily terminated, which would be much harder.

You really need an attorney to prepare the adoption petititon. The attorney will advise you what steps to take.