Violence among family members used to be one of those things nobody talked about.

But that began to change in the mid-'60s as one after another form of familiar violence and abuse was exposed. First the focus was on child beating and abuse, followed by attention to sexual abuse of children in the early 1970s.

The focus in the mid-'70s turned to wife beating is becoming a topic of discussion.

Next, according to sociologists, attention will turn to the problems of sibling abuse (both physical and sexual), parent abuse and finally the abuse of the elderly, which the British call "granny bashing" or "gram slamming."

Violence always has been an integral part of family life, according to sociologist Richard Gelles, associate professor of the Department of Sociology and Anthropology at the University of Rhode Island.

"The family is the most violent group in society with the exception of the police and the military," Gelles said.

"You are more likely to get killed, injured or physically attacked in your home by someone you are related to, than in any other social context."

The FBI reports that domestic violence is the most common and the most unreported crime in the United States. An estimated one-quarter to one-third of all homicides are domestic murders in which one family member kills another.

A survey of 2,143 families conducted by Gelles along with Murray Straus, director of the University of New Hampshire's family violence research program, and Susanne K. Steinmetz, an associate professor of individual and family studies at the University of Delaware, disclosed startling statistics. Projected nationwide, the survey's results showed that all the victims of family violence - children, wives, husbands and parents in 1975, the year surveyed - would amount to the population of New York City.

"About 8 million people, and everyone of them getting either struck, stabbed, beat up, punched or kicked at least once a year," Gelles said.

"There are more battered spouses alone, the survey indicated, than there are people who live in the city of Los Angeles. If violence were a communicable disease like swine flu, the government would consider it an epidemic."

But the effect of violence amont family members does not confine itself to the members of the family. The FBI estimates that about 20 percent of police deaths and 28 percent of assaults on police officers occur while officers are intervening in family fights.

Barbara Star, a professor of sociology at University of Southern California's School of Social Work, concludes "You are probably safer on the streets of Los Angeles at night than you are in your own home.

"Sharing a residence increases the chances of multiple physical violence and you can't avoid it." That is not to say that today's families are all bad.

"There is a kind of paradox about the family as there is with so much of life," says sociologist Straus, "I characterize the family as the most violent group a typical citizen has anything to do with, but at the same time, it is also the most loving and supporting group. And those two things, that combination and how those elements coexist, is what research is trying to unravel."

Until recently, little research has been done on family violence.

One reason was that there is a kind of implicit rule that gives people the right to hit a member of their own family. The clearest example of this is that parents have the right to hit children and the same is true of sibling fights - they are expected, Straus says.

"Even with husbands and wives, the marriage license is a kind of hitting license," says Straus.

"Violence can be used for normally good ends - that's a fundamental part of our thinking - that's why we go to war." However, there is no such right (implied or otherwise) in the case of incest and abuse of the elderly. The rules of society expressly forbid incest and frown on abuse of the elderly. Yet all three types of abuse and violence occur and they affect every member of the family.

Most experts agree that the amount of violence in the families has decreased since colonial times, when both wives and children were considered chattel.

But they also say that family violence is more deeply hidden than in years past.

"You can get away with so much more violence in the family because the family unit has gotten smaller," Star says.

"The family has decreased in size and visibility. There is nobody around to censure you, not even your family and that's been a real key factor in what is going on in homes and why it doesn't get stopped.

The Gelles, Straus and Steinmetz survey found that the rate of child abuse is 129 percent higher in families where there is also spousal abuse.

As a result of the study, Gelles projects that between 1.4 to 1.9 million children were subjected to physical injury in 1975, the year covered by the survey.

Jerry P. Flanzer, director of the Mid-America Institute on Violence in Families at The University of Arkansas, adds that another contributing factor in child abuse is alcohol - 70 percent of all family violence is related to alcohol consumption.

A separate category of child abuse is sexual, including incest.

It is not violence in the technical sense in most cases, but it is intimidation or emotional force - an older person using his position of authority or trust to get a child to engage in sexual activity.

David Finkelhor, a research scientist on the family violence research project at the University of New Hampshire, has just completed a survey in which 800 college students were asked about their childhood sexual experiences, especially those in which they were victimized by adults or adolescents.

About 19 percent of the women and 9 percent of the men had had such experiences when they were children," Finkelhor says. "And interestingly enough a large number were family members."

Finklehor's study found that with girls, the experience was usually a relative and with boys it was usually a neighbor or other acquaintance.

In almost every case the older partners for boys and girls were men. "There were very few cases of adult women taking sexual advantage of children," Finkelhor said.

In this as in other studies, father-daughter incest was one of the most common forms. Finkelhor and others estimate that about 1 percent of all women have some sort of father-daughter sexual experience.

There are many reasons for sexual abuse of daughters by their fathers but one of the most common, according to Henry Giaretto, director of the sexual abuse treatment program for the juvenile probation department of Santa Clara County in northern California, is a need to be loved and accepted by someone in the family.

The relationship is usually preceded by the man losing his job or being faced with some other low point in his life that reduces his sense of self-esteem, says Giaretto.

He and his wife are drifting apart and he turns to his daughter, who is usually about 10 or 11 years old, for comfort. Another familiar scenario, according to professor Star, is that the marriage is falling apart and the child is sacrificed to keep it afloat.

"The child is the victim. She is pushed forward by her mother as a surrogate wife," says Star.

After child abuse, the most obvious form of family conflict is spousal abuse.

"In any one year, says sociologist Straus, "one out of every six couples will have some kind of physical altercation - that ranges from slapping or throwing things, to using a knife or gun."

Until recently, the popular belief was that husbands were the assailants and wives the victims. But according to the Straus, Gelles and Steinmetz survey, wives are just as abusive.

"If your criterion is who ends up in the doctor's office or hospitals, says Straus, "the husband is quite rare compared to wife abuse because men have larger muscles and are on a average 2 to 3 inches taller.

"But if the criterion is the number of acts considered to be violent carried out by the participants, like throwing coffee pots, then husband abuse is an equally serious problem.

"Our data, as well as that of three or four other studies, shows clearly that men and women have roughly equal rates of that kind of abuse," says Straus.

Husbands and wives are also about equal when it comes to murdering their mates.

According to 1975 FBI statistics of spousal homicides, 7.8 percent were husbands while 8.0 were wives.

According to Geraldine Stahley of Womenshelter, a haven in Long Beach, Calif., for battered wives and their children, 80 percent of the men who batter their wives were battered children or were children who watched their fathers beat their mothers. Women who tend to stay longest in these relationships are very traditional women who are strongly attached to the role of wife and mother and feel it's their responsibility to make their husbands and homes happy.

They are embarrased to seek help because they feel it means that they have failed.

And sometimes they are just afraid of what will happen if they turn their husbands into the authorities, says Stahley.

Sibling abuse, parent abuse and abuse of the elderly, are areas that are just beginning to receive attention.

Susan Steinmetz, who has made some preliminary studies in this area, estimates that between 63 percent and 78 percent of all Siblings used physical violence to resolve conflicts.

The Steinmetz Straus and Gelles survey found that of families with two or more children between the ages of 3 and 17, 75 percent reported Sibling violence an average of 21 times per year; 38 percent kicked or hit; 14 percent beat up a Sibling; .08 percent threatened with a gun or knife, and .03 percent actually used a gun or knife.

The Finkelor study also found that 13 percent of his interviewees had had some kind of sexual experience with a sibling.

Of those who had, one-third were before the age of 8 and one-third were cases where substantially older youngsters took advantage of younger children.

The National Office on Aging says that it has set abuse of the elderly as one of its topics of research this year, but it does not have any statistics yet.

Steinmetz believes that most of the abuse takes the form of "such things as tying the elderly person who needs constant watching to the bed in order to do shopping or housecleaning or using excessive amounts of alcohol or sleeping pills to keep them under control."

But, she added, battering of parents with fists and objects to make them mind or to change their wills or their financial arrangements, is unfortunately a growing phenomenon."

Without help, said another expert, Star, the family "is a social institution that is destroying itself from within."