I need help protecting my siblings, what do I do?

As long as your parents are still legally married, each parent has the right to take the children anywhere he or she pleases. It is only after divorce and with a court order determining the parental custody rights and prohibitions can a parent be restrained from taking the children out of the jurisdiction of the court. One thing to keep in mind is that if the children are all American citizens the country of Mexico requires the parent attempting to enter Mexico with children to have the legal authority to take the children into Mexico, either by court order or a certified letter from the absent parent that the trip is approved. So, it's not so easy to flee to Mexico with American children. Still, your mother needs to file for temporary custody as soon as she is released and she must ask for a travel restriction to be placed on movement of the children. If you know where the passports for the children are, then maybe you should hide them very well.