They need to do a Bible study on anger. Why are they angry in the first place? Maybe the root causes of anger need to be established.
Cabopolonio, are your family members Christians? If they read some Bible verses about anger and peace, or harmony with others, that will probably help. May be loving one’s neighbor as oneself. It is the word of God that changes us. I have seen that in my own life. When you meditate on it, things begin to change in your character. That would honestly be the best course of action for you. Good luck.
Cabopolonio, I am praying for your family