FaceTime calling wrong person

When I FaceTime my wife it always seems to go to my mother in law. I will dial my wife on a call and when in the middle of the call I click the FaceTime icon and then all of a sudden I'm talking with my mother in law instead of my wife. It happens with FaceTime audio as well. My wife will say it rings but she's not able to accept it. None of her contact info has my mother in law on it. What is going on? How can I actually FaceTime my wife without it going to someone else?