I have a brother that's put my family through the wringer time and time again, so I can understand what your family is going through.
You can't help but worry about the kids. You never know what they are being exposed to when the parents aren't stable. and you hate for them to grow up thinking that all the conflict is a normal way of life...
Thankfully she has you, and I understand your wanting to protect her as much as you possibly can.
Follow your heart, Monica, and may God bless you!