I as an older sister see my father using his strenghth to hurt my younger brothers with out any proper reason. Do I have any right to say anything when I see it should I just ignore it ? I think that as a result my little brothers are more violent amongst themselves and with other kids.

The commandment "Lo Ta'amod Al Dam Re'echa" - "do not stand by while another's blood is spilt" (Vayikra 18;16) applies to preventing physical and psychological damage. This overrules the commandment of honoring one's father, though does not allow speaking in a way that is abusive, or disrespectful if a respectful intervention will suffice. You are not obligated to put yourself in any danger. If you believe your brothers are in danger, you may want to consult with a professional person (social worker, school guidance counselor, family doctor) for suggestions. If necessary, asking for outside intervention should not be ruled out.