Great news for the long run! People like her love to nail their own coffins shut. Do you know if she was legally served a summons of the hearing today? There is a good chance the children, if found, will be taken into protective custody by the authorities until this is legally resolved, if so, they may appoint a guardian ad litem for the children, which is key. Your brother's mantra should then be, "I only want what is in the best interest of the children," (they love this) over and over and over. Pursuade the guardian to request a psychological evaluation of the mother.
Thanks for the update. She doesn't sound well. Prayers for the children, a sound court ruling. Gotta run. Have a good weekend and let us all know how it eventually turns out...