Best wishes and prayers to your family. Hopefully, he is well represented.....here is a HUGE recommendation, especially if he is not successful in today's attempt. If this has not already been done tell your brother to work towards a COURT ORDERED psychological evaluation of the mother.
This is on-the-plate, so to speak. My brother seems to have a good attorney (she's Christian as well), but the problem will be getting the court to recognize and admit the evidence my brother has discovered, because my sister-in-law will probably fight having a psych eval.
He should ask for a "Court appointed special advocate"...then mention that the mother has psychological problems, and he would gladly submit to the same psych exam he is suggesting for her.
Keeping in mind that his psych exam would show the stress of the last month, but that it should also show that it is related to the sudden disappearance of his children. Mine showed a slight personality disorder with depression- specific (...which means "there is a reason for it")...his came back with a higher level of personality disorder-non specific.