I don't want to live with my mom and she's legally married to my step dad, how can he get custody?

You need to ask your dad if its possible to apply for custody of you because you want to be in his house but he is going to have to agree to take you.That would be the better option to take you just got to see if you can stay with him on a ongoing bases thats where you have to start you have to work it out with mom and step dad.You can ask a judge to put you with your step dad?