Looking for some custody advice

Y’all, please be kind. I have NO idea where to start with this whole situation, and am looking for advice from those who have been in these shoes, or similar. ❤️

My boyfriend has 2 children by his ex. Recently, She moved them out of state, and has cut off all contact with their dad. We had no idea where she was, and unfortunately they don’t have a custody order because things had been civil until she disappeared.

She recently came back into the state, and is now in jail for something unrelated to us. She has child cruelty charges, among a few other things. The little girls have been with a family member on their moms side, who hasn’t been in contact with us either.

Where do we start as far as their dad getting custody of them? I am waiting on a call back from a lawyer in the area, but haven’t heard from them yet, so I’m clueless.. my hands feel tied.

Does anybody know what the first step needs to be? Or the second, or third?