+1 on the fault is fault thing
the lady could have been high, drunk, trafficing illegals, selling narcotics, and have no license, your brother was still at fault for the accident. Your insurance company will pay her the damage to her vehicle and then look at a BI claim (bodily injury) If she is claiming injury for her children who werent in child restraints and the child restraints could have prevented those injuries, chances are she will get diddly squat for those injuries, because that shows some comparative negligence on her behalf. If she wasnt wearing a seat belt, it factors against her. 80% talk a whole lot of shit at an accident scene (trust me I hear it day in and day out as an auto claims adjuster) If they do seek an atty representation chances are it will get settled out of court. If for some reason it goes to litigation (which your brother's insurance will pay for the defense), it will still most likely get settled for well below his policy limits even if he does carry minimum. from what you said the lady got out of the car and immediatly started mouthing off. she wasnt transported to the hospital. I guarantee you shes gonna claim soft tissue injury stuff. and pending on where it happened if it ever does go to litigation, if she's in the DFW area chances are she's not gonna get much money because the DFW area is a venue that is pretty conservative in injury payouts. if its down in the rio grande valley, she may get more, but chances are your brother's insurance will get it all taken care of without much stress on his behalf
Its a crappy situation, chances are the lady will get fined out the wazoo for no DL, No inspection yadda yadda yadda,she'll probably not show to court and a have a warrant put out for her arrest and not much will become of it because if she goes to court the court knows how to reach her and then make her settle up on the other crap she skipped out on.