Can someone help me in this situation..?

I have an auntie and three cousins and all of them are being emotionally and physically abused by their her husband/ their dad. I don't know what to do I have been told off other family members just to forget about it and thats just the way he is but it is always on the back of my mind. I hate knowing that they are living in the same house as that ********. I want to phone the police but i'm uncertain of the outcome. One of my older cousins who is now 18 recently told me that he threw her on the floor and attacked her. This is serious and i am really worried. Someone please tell me what I can do.