How can a single mom win a custody case against the father who got remarried?

Today my mother, brothers and sisters we're about to move. My mom left to put boxes in storage and so did my granddaddy. The police show up with my dad's wife who made the call. She said that we called in the middle of the night saying we were hungry, scared, and didn't want to stay in the house. Now this is what happened. My mom comes home, my dad's wife straight up says that she wants our birth certificates and social security numbers cause she is taking us now. Now, all of this didn't happen cause neither of us had a phone. I didn't have my phone since last May and that was before my dad moved in, even met that woman, too. Now she is saying that my mom is giving money to her boyfriend, feeding his kids and all this kind of stuff. The officers didn't do anything except the black one. The rest were white. Her boyfriend cusses her out but they tell him to back off but they didn't do that to her. Now I'm staying with mom. I'm fifteen, the kids had to go with the woman. Somebody tell me what should we do, because they will do an investigation tomorrow.