It may be easier, at the moment, to speak to a counselor at an abused women's shelter.
I'm making the assumption, that for whatever reason, your mother is unwilling, or unable to make changes to protect herself, and her children.
As you have described the home situation here, when explained to a counselor, she will see that your mother would certainly 'qualify' for assistance. Whatever the needs are, there are resources to help and protect women and their children in their care.
Once it is established that you and your sister are in need of protection, they will also be able to provide resources. I think this is an immediate need here, and I encourage you to seek this type of assistance.
Because there has already been police intervention (were there charges laid, and do you know what they are?), and that wasn't enough to slow your step-father down, it is necessary for you to think of yourself and your sister only.
I hope that it doesn't escalate to a point where in the not too distant future that you will also find yourself protecting your mother, and in so doing, get injured yourself. It is an impossible situation for you being so young, to be the protector, instead of the protected.
But it is what it is. Have confidence that taking steps will help, not hurt, your situation.
It may take time to contact relatives in Canada, let alone arrange to have help from them. I think that intervention by family could very well make things worse, as abusers would prefer to keep their abuse private, and particularly if they can only provide phone contact with your mother. She may be in further danger by involving 'outsiders'. I don't know enough about your situation to say whether that is a good option at the moment.
But I do know this. The better informed and educated you are as far as what you CAN do and what your options are, the better you and your sister will be.
