Chapter 9

IT’S NOT EASY FOR ANY child to survive the teen years without making at least a few poor, dangerous, sometimes even life-wrecking choices. Complicating things is the oddly bacterial nature of bad behavior. Sexual adventurousness, substance abuse, even petty criminality—all can seem thrilling to kids and teens, spreading readily among them like a contagion, with peers teaching peers and schoolmates influencing schoolmates far more persuasively than parents and teachers ever could. But in study after study, the most irresistible influencers of all are siblings.

Brothers and sisters—particularly older brothers and sisters—are permanent, live-in, total-immersion mentors. Younger brothers and sisters whose older siblings drink are twice as likely to pick up the habit themselves and, when it comes to smoking, four times as likely. Drug use, truancy and delinquency also increase in lockstep from brother to brother and sister to sister, as with the likelihood of teen pregnancy.

Sibling influence has its limits, of course, and probability isn’t certainty. If it were, there would be no families that have both sober sibs and drinking sibs, smokers and nonsmokers, graduates and dropouts. There are a lot of other variables at work, such as gender, age gap, family income and education. Sibling influence can even flow both ways, with a younger brother or sister teaching bad habits to an older one. And even when sib-to-sib influence is at its most powerful, those influences needn’t always be negative ones. If it’s true that siblings can steer one another into danger, it’s also true that they can steer one another out of it, playing a role that’s not corrupting or destabilizing but healthy, therapeutic, even wise. The question is which way any one sibling group will go—and the answers are never easy to predict.

Of all the risky behaviors siblings can share, it’s the teen-pregnancy piece of the puzzle that’s perhaps been the most studied. That’s partly because it’s a problem that’s so amenable to intervention. Avoiding temptations such as tobacco and drugs is a job that takes a lifetime, since the substances are always there—although if you make it through your teen years without ever having tried them, it’s much less likely that you ever will. But pregnancy is something that merely has to be delayed for a while.

The U.S. has done a good job of keeping its teen birthrate in check for the past generation. Currently, there are about 41.5 births per 1,000 girls in the 15-to-19 age group. That represents a decline of more than 20% in some demographic subsets from 1991 to 2005.

Patricia East of the University of California, San Diego, has been a leader in the field of kids, sibs and risk behavior, and much of her focus has gone to pregnancy, particularly in the Hispanic and African American communities, where the rate of motherhood among teens is generally higher than in the broader population. A great deal of this increased incidence is due to lower income and reduced educational opportunities, but family dynamics also play a role, and East and her colleagues set out to investigate that part of the puzzle. Tracking 127 volunteer girls over a six-year period, they focused principally on the influence of the two most powerful female figures in the girls’ lives—their mothers and their older sisters. Some of the subject girls’ moms had been teen mothers; some of their sisters had; in some cases the family had no history of teen pregnancy. The influence these differing backgrounds had was powerful—and unmistakable.

Girls in East’s study with an older sister who had a baby as a teenager were 4.8 times—or 480%—as likely to become pregnant in their teen years themselves. If a girl’s mother and sister had both been teen moms, the figure rose a bit higher, to 5.1, or 510%. But if her mother alone had had a baby in her teens and her sister had not, the younger sister’s risk rose by just 0.2, or 20%—significant but not startling. The study suggested a lot of explanations for the results, some more obvious than others.

If it’s true that siblings can steer one another into danger, it’s also true that they can steer one another out of it.

Little sisters have a ringside seat to the exciting adventures of their older sisters, so it is no surprise that, for better or worse, they so often follow in their footsteps.

For one thing, to an adolescent daughter, what happens in a mother’s teen years is long-ago history. It’s something she wasn’t around to witness herself, which dramatically diminishes its impact. What’s more, the mere fact that it’s part of her mother’s biography makes it less appealing to a teen girl trying to establish her own identity.

But from babyhood, little sibs mimic big sibs and often keep right on doing so as they grow up. “Siblings train each other; they influence each other,” says Jennifer Jenkins of the University of Toronto. “A person is fashioned from all these small things.”

In the first year after the birth, 80% of teen mothers continue to live at home, and 50% are still there after two years. This means big changes for the little sister. The older girl is now doing very adult things—feeding, changing and caring for a baby—while the younger girl is still expected to be occupied with school and curfews and other juvenile concerns. Regardless of age, siblings will always jostle for position in the nest just as they did when they were small, and when one child rises in station, the other will try to keep pace. “[The older sister] is given adult status and more power,” East says. “She issues orders to the younger kids in the family such as ‘You will help me with the child and babysit.’ It changes the dynamic between siblings.”

The only way for the little sister to attain the same rarefied position is to become a mother herself—and not only does it seem like an attractive possibility, it also becomes a somehow more tolerable one. Unless the teen mom was tossed out of the house when she became pregnant, the fact that she’s now a mother may seem to have been endorsed. “The older sister has opened the floodgates on what’s acceptable behavior,” East says.

Even in homes in which becoming a teen mother remains manifestly unacceptable after an older sister gives birth, other forces are at work to push the younger sister in the same direction, like having a mother now distracted by caring for the new baby.

“These new grandmothers start to be more distant from the younger sisters,” says East. “The girls report that their mothers are less available, less supportive, and that they talk less and spend less time together than before.” A more remote mother is one less able to keep track of a little sister’s whereabouts—and a little sister who’s out on her own is walking squarely into trouble.

Still, the fact remains that most such girls do manage to avoid that trouble. Even in the higher-risk populations East often studies, only 36% of younger girls follow their big sister’s pregnancy path, which means that 64% don’t. One key factor at work here is the age gap, with girls who are just a year or two younger than their big sisters generally facing a lower risk. The reason might be that the closer in age the younger girl is, the likelier it is that she’ll have to help out with the loud, messy, smelly business of baby care. In some cases, at least, this can be enough to scare her straight—though during the golden period when the entire family is enchanted with the baby, it may have the opposite effect. What’s more, close-in-age younger siblings are, as a rule, less in thrall of the older one than sibs who are, say, five or six years behind. That makes emulating the older sib a little less appealing.

Younger brothers and sisters whose older siblings drink are twice as likely to pick up the habit themselves.

East conducted a five-year study of 227 families and found that those girls who did not follow their older sisters into premature motherhood were more than just lucky; they were often consciously careful. “[The younger sister] purposely decides to go the other way,” says East. “She decides her sister’s role is teen mom and hers will be, say, high achiever.” None of this discounts the very proactive role the parents can—and often do—play in helping the younger sister avoid premature parenthood, even with the distractions of a squalling baby in the house. At the same time that more domestic attention goes to helping the teen mother and her baby, more disciplinary and academic attention may go to the younger sister, who is seen as the family’s next, best hope for a child on the high-earning professional track.

In one study of families with multiple risks of teen pregnancy, up to 80% of younger girls whose mothers did not monitor them closely followed their older sisters into teen motherhood. Among families in which parents cracked down, the figure was cut nearly in half, to 42%.

If pregnancy were the only risk behavior siblings pass around like seasonal flu, parents’ lives would be much easier than they are. But the same dynamics that drive imitative childbearing are also behind shared problems such as alcohol, tobacco and drug use. Actually, in those areas, the behaviors among siblings are even more contagious, because boys and girls may be equally affected by them and, more so than in pregnancy, the influence runs from younger to older almost as easily as it does from older to younger. Of all the substances kids can abuse, tobacco is the toughest to regulate. It’s both a legal product and, while its sale to minors is prohibited, the law is still widely flouted. That’s a dangerous convergence of appetite and availability.

The fourfold increase in risk that younger brothers and sisters face when an older sibling smokes is a stubborn problem that endures even as the overall rate of smoking in the U.S. has plunged to a historic low of less than 20%, according to a vast sampling of 11,406 kids and young adults from age 14 to 22 called the National Longitudinal Survey of Youth. A study conducted later in Australia produced the same findings, with 40% of kids whose older sibs smoke taking up the habit themselves, compared with 10% of those with nonsmoking sibs. Not only do the younger brothers and sisters follow older ones into tobacco use, they start younger too, often lighting up shortly after the first time they see a big sib with a cigarette.

Gender differences turn up as well. Tobacco use spreads faster from brother to brother and sister to sister than it does across the brother-sister divide. This, again, is partly because the social circles of opposite-sex sibs are less likely to intersect. But even within same-sex circles, the risk is not equivalent. Despite the historically higher incidence of tobacco use among males, brothers are a little less likely to influence one another to smoke than sisters are. Psychologist Joseph Rodgers of Vanderbilt University believes this is probably the result of the greater openness girls exhibit among themselves, which can be a very good thing when it comes to sharing feelings, fears or confidences but a very bad one when it comes to sharing cigarettes. Drugs and alcohol follow a nearly identical contagion pattern, though the spread is a little bit slower and a little less reliable.

Psychologist Elizabeth Stormshak of the University of Oregon conducted a study in which she recruited teen and adolescent siblings and instructed them to role-play on videotape. They were told to pretend they were planning a party, that some kids might be bringing drugs or alcohol, and that they should discuss whether that was appropriate or not. Predictably, when a scientist is watching and a video camera is rolling, nearly all of the subjects began by saying that, no, it was not all right and, no, they themselves certainly wouldn’t try drugs, no matter what. But those first answers were not what Stormshak was interested in—and they didn’t always remain the answers anyway. Sometimes the older siblings would waffle a bit—coming around to the possibility that experimenting with a substance might be all right if other kids were doing it and if they tried it only once. That quickly became the younger siblings’ position too. If the older sib remained adamantly opposed to drugs and alcohol throughout the role play, the younger kids did as well. How well the kids got along was a factor too. “When siblings are very close,” Stormshak says, “that relationship becomes more powerful and meaningful and can enhance risk behavior as well.”

Other kinds of criminal behavior—theft, assault and drug dealing, as opposed to personal use—are nastier matters. Psychologists and sociologists closely study the phenomenon they call “delinquency training,” particularly in low-income families, in which rates of criminality are the highest. A lot of the expected findings have turned up in their work. Brothers pass criminality back and forth more readily than sisters do, but girls are not immune. Opportunity and exposure are powerful variables, with younger siblings likelier to get into trouble with the law if they spend time with an older brother who has already crossed that line, or who is part of a social circle whose other members have. Some studies have also shown that brothers who have a shared history of physical violence—fighting with each other in ways that go beyond the routine blows all brothers and sisters exchange—will become accustomed to resolving conflicts as aggressively, and this will contribute to violence outside the home.

Not all sibling relationships are so troubled, of course, and far from leading little brothers and sisters into trouble, many older sibs consciously—even aggressively—steer them away from it. This may be especially so in the case of substance abuse, particularly among families living in communities where the dangers of drugs are especially pronounced. Frederick Gibbons, a professor of psychology at Iowa State University, tracked 900 African American families in Iowa and Georgia from 1997 to 2006, using questionnaires and observation to study the proactive role non-drug-using older siblings sometimes played in keeping younger members of the brood clean, and found that when the sibs do take such initiative, they can do a remarkable amount of good.

“The younger siblings won’t necessarily drop friends who are using drugs,” Gibbons says, “but their own use is greatly affected by whether their older sibling has a negative attitude about drugs. There is a kind of ‘just say no’ effect going on if it comes from the older sibling.” Parents play a role here too, of course, but what struck Gibbons is that it’s often a secondary one. “Between the two—parents and siblings—the siblings’ role is often the more influential one.”

Brothers and sisters may be good at cracking open one another’s defenses and denials, muscling a wayward member of the brood into better, healthier behavior—and sometimes that’s precisely the thing that’s needed. But they’re also good at the subtler business of gently picking one another’s locks, feeling how the emotional tumblers fall, and opening a sibling up in a way no professional, or even parent, ever could. There are two parts to the idea of tough love, and well-bonded sibs can practice them both.

Sibling Barbarity: What Drives Brothers to Terrorism?

The sibling bond can be a powerful force for good—until it turns deadly

The terrorist attack at the headquarters of the French weekly Charlie Hebdo in Paris was the work of two brothers: Cherif Kouachi, 32, above left, who was said to be the leader, and his brother, Said Kouachi, 34.

THE JANUARY 2015 MURDERS AT THE OFFICES of the French satirical newspaper Charlie Hebdo were a case of darkness wrapped in darkness, with multiple layers of horror. There was the hijacking of a religion, the threat to free expression and, of course, the killings themselves, methodical executions conducted by pitiless gunmen.

Central to all of that is the mystery of the people who police believe carried out the killings—no different in some ways from terrorists who went before them except in one critical way: they were brothers. Cherif Kouachi, 32, and Said Kouachi, 34, both French citizens, were the central targets in a manhunt that spread across France before they were killed in a police raid.

The drama played out at the very moment that, 3,500 miles away, Dzhokhar Tsarnaev, 21, was standing trial for the Boston Marathon bombing, an act of terror he was eventually convicted of committing in 2013 with his older brother, Tamerlan, who was killed in a shootout with police.

That, inevitably, raises questions about the sibling bond itself. How do the Tsarnaevs and Kouachis compare with other wicked siblings, like Lyle and Erik Menendez, who murdered their parents in 1989 in a case that became a national obsession? Are they all merely outliers, bad characters who would have each done wrong no matter what? Or is there a particular power the sibling relationship has to hothouse the worst traits in the people who are part of it?

One thing is certain: brothers and sisters influence one another’s behavior in a way that no other person in their lives—not parents, not teachers, not friends or spouses—seems to be able to, especially when it comes to bad behavior. A younger brother or sister is twice as likely to drink and four times as likely to smoke if an older sibling has already picked up the habits, studies have shown. “Having an older sibling exposes you to things firstborns simply aren’t exposed to,” says Susan Averett, a professor of economics and a siblings expert at Lafayette College. “You see things you wouldn’t otherwise have seen. In some ways your innocence gets taken away.”

Smoking and drinking, of course, are behavioral misdemeanors. But older brothers and sisters can lead their little sibs into much larger crimes too. Theft, assault, drug-dealing, even murder can all be part of a sibling-to-sibling legacy that psychologists and sociologists call “delinquency training.” It doesn’t take long for learned behaviors to become permanent behaviors—even if the siblings drift apart. “Siblings train each other, they influence each other,” says psychologist Jennifer Jenkins of the University of Toronto. “A person is fashioned from all these small things.”

Even true felonies, of course, are nothing compared with what the Tsarnaevs and the Kouachis allegedly did. For that kind of savagery, you need something more—and typically that something is grievance, a shared sense of being wronged, which the siblings echo back and forth to each another. Dzhokhar Tsarnaev, a Chechen immigrant like his older brother, was a scholarship student who wanted to study nursing and was described by his friends in all of the ways people who wind up doing something terrible often are—generous, compassionate, never showing a sign of trouble. Tamerlan, on the other hand, never quite adjusted to life in the U.S. and retreated further and further into isolation and resentment. But he did have Dzhokhar, and once Tamerlan began flirting with jihad in 2011, it might have been relatively easy for him to bring his little brother around.

If the Kouachis underwent a similar radicalization, reports suggest it was younger brother Cherif who took the lead. Cherif had already spent time in prison in 2008 for being part of an organization that was recruiting jihadis, while Said’s rap sheet was said to be clean. Both brothers were in Syria in the year before the attack, however, and might well have come back radicalized. It is a sad fact of this latest human atrocity that the sibling relationship—which can be one of the richest and most nurturing of all—may have been the source of so much suffering.