Violence in the family often follows other forms of more subtle and long-term abuse: verbal, emotional, psychological sexual, or financial.
Violence is closely correlated with alcoholism, drug consumption, intimate-partner homicide, teen pregnancy, infant and child mortality, spontaneous abortion, reckless behaviors, suicide, and the onset of mental health disorders.
Most abusers and batterers are males - but a significant minority are women. This being a "Women's Issue", the problem was swept under the carpet for generations and only recently has it come to public awareness. Yet, even today, society - for instance, through the court and the mental health systems - largely ignores domestic violence and abuse in the family. This induces feelings of shame and guilt in the victims and "legitimizes" the role of the abuser.
Violence in the family is mostly spousal - one spouse beating, raping, or otherwise physically harming and torturing the other. But children are also and often victims - either directly, or indirectly. Other vulnerable familial groups include the elderly and the disabled.
Abuse and violence cross geographical and cultural boundaries and social and economic strata. It is common among the rich and the poor, the well-educated and the less so, the young and the middle-aged, city dwellers and rural folk. It is a universal phenomenon.
1. http://www.lundybancroft.com/pages/articles_sub/CUSTODY.htm - Understanding the Batterer in Custody and Visitation Disputes