Brother in very toxic relationship.

[Anonymous]

I would as others said:

1. support them emotionally, have them come for trips and call and skype a lot. try to find them local resources, best friend's mom etc. that you can talk to and explain so someone there can swoop in.
say there's fighting in the night, the kids can no questions asked go to johnny's for a sleep over.

2. call the school. if nothing else given a mom that is passed away, these kids need advocates and teachers at school to be aware. this is very common, bad home life.
you need the kids to be in touch. if you explain it, the guidance people can talk to the kids without them being in formal therapy etc. with Dad's permission.

if you can't get them out and keep the kids, just try to make sure they have the best support around them and encourage them to keep up school etc. so they can get out of there as soon as they graduate.