'Sibling Effect:' Mom Has a Favorite and Birth Order Counts

Author Jeffrey Kluger analyzes birth order, twins and singletons.

Sept. 30, 2011— -- At age 4, Bruce was small enough to stuff into his family's Baltimore basement fuse box – an old-style cabinet filled with "high-voltage, old style unscrewable fuses." His three brothers convinced him it was a space capsule, "just like Alan Shepherd's."

His older sibling, Jeffrey Kluger, now 57, admits it was an act of mischief, but also protection for the most vulnerable child, as they hid from their volatile father and, though they didn't know it then, their prescription drug-addicted mother.

Brotherly love -- and its accompanying intense rivalry -- is a topic close to Kluger's heart. In his latest book, "The Sibling Effect," Time's senior science writer takes a scientific -- and personal -- look at what he calls the "last unexplored frontier of family relationships."

"It was only years later that I would go a little cold, thinking about the deadly danger we courted on those mornings, squeezing a small child and high voltage so close to each other," he writes.

The four Kluger boys – five years between oldest and youngest -- propped each other up emotionally throughout the multiple divorces of their unstable parents. Their mother was married twice, bringing two stepsisters into the mix.

Their father remarried and had fraternal twins, giving them two half siblings.

"One of the points I make in the book that when the parents, who should be the anchors of the family, come unmoored, the kids do what people do in a fox hole," he told ABCnews.com. "We pull together."

But they are also fierce competitors and partners in crime. "My brothers and I played boisterously, fought frequently, and broke things constantly," writes Kluger.

Siblings are the ones, of all relatives, who share the longest stretch of time on earth, are more important than parents, children and even friends.

"Our spouses and children arrive comparatively too late in our lives; our parents leave us too early," according to Kluger, who quotes family sociologist Katherine Conger of the University of California, Davis. "Our brothers and sisters are with us for the whole journey."

The book, a memoir woven with relevant scientific research, explores every imaginable aspect of the sibling relationship: favoritism, birth order and even why brothers and sisters are not sexually attracted to each other.

Not only do our siblings smell too familiar to have sex with them, explains Kluger, they are a product of the "kibbutz effect," where growing up in close quarters tends to kill any physical attraction.

Siblings are by nature -- and he provides many examples from the animal world -- genetically programmed to be a "team of rivals."

Kluger confirms earlier research that shows first-borns and "singletons" do, indeed reign supreme. Both groups are smarter and more economically and emotionally successful than the middle child or the baby.

But he also debunks some long held myths. For starters, all parents have favorites.

"One message I have for parents is that they should quit feeling guilty about having a favorite," he writes. "I like to say that 99 percent of all parents do have a favorite child and the other one percent are lying through their teeth."

But that, he writes, is not always a good thing: Although less-favored children have lower self-esteem, the favorite can have a harder go of it in the real world. Favorites can be thin-skinned when it comes to criticism and "unprepared for having to prove themselves," said Kluger.

"History and drama are full of examples of the favored prince who got into the world and couldn't function because he was not accustomed to an environment where he was judged more objectively," he said. "They tend to get a real waking up and a humbling in the world."

Favorites also take more heat from their siblings, according to Kluger, which can make home life miserable.

Kluger also says fighting is nature's way of competing for food and our parents' attention. "We are also genetically driven to show off our strength and general fitness -- another way to ensure that our parents will love us and look after us," he said.

Not surprisingly, even well-adjusted children ages 3 to 5 will have up to seven fights an hour.

Kluger also addresses the much-maligned only child. Not only are they smarter, but they are more self-sufficient and have more "sophistication," because of all the adult company. With modern day care and play dates, many get just as much socialization as children with siblings.

"They are living in a world in which no one cares about picking sides, where there is no favorite," he said.

Research on birth order remains constant. Firstborns are the highest achievers with IQs that are on average 1 to 3 points higher than the next sibling. In addition to being physically larger, they also become the biggest earners.

"Younger siblings tend to be the charmers, the adventurers, the comedians and the rebels," said Kluger. "Middle siblings take longer to find their identity."

They grow up at the mercy of their older siblings and experience much of what Kluger's baby brother Bruce had to endure.

"My brother force fed me caterpillars when I was little," said Lisa Palmer, now 61 of Glastonbury, Conn. "My mother told me that he never got over having to share her with me."

Jeannie Pierce, 57, and the younger of two sisters from Shrewsbury, Mass., said her sister pushed her carriage down an incline and the 6-month old fell out and suffered a concussion.

"She also stuck gum in my hair so my mother had to cut it real short," said Pierce. "She also locked me in the cellar during a thunder and rain storm, during which I cut my wrist open banging on the door window."

Much of the turmoil, just as in the Kluger household, was carried on under the radar of their parents.

Pierce's jealous older sister, while charged with babysitting, left her 8-year-old sibling at home so she could go to a dance. She also chose the bed by the window and made her little sister sleep by the door.

"Her rationale for this was that, if someone broke in and tried to murder us, she would be able to escape out of the window while I was being murdered," said Pierce.

One older sister is quick to confess that she made her younger sister's life hell. "Oldest siblings eventually know the truth," said Susan, a 61-year-old first-born from Portland, Maine. "We are all recovering tyrants."

"The family story goes that when our parents told me that they were so excited that they were having another baby, I said that that sounded great as long as we could 'get rid of that one,' my sister Laura."

Kluger's research affirms that middle siblings may not get showered with the same adoration, but they often have better relationships and more independence as they grow older.

They are also more empathetic.

"We learned from you," Laura, 59, from Oakland, Calif., said of Susan and other first-borns. "And then we set that aside and took our own places, informed by what we had seen... Today, we are about the same age and we face our mortality and our wrinkles and losses and our looming old age together."

Not all siblings end up as friends. One large study revealed that about 15 percent have relationships that are beyond repair, "broken and badly fraught."

At the heart of Kluger's message is that as we age, strong sibling relationships can keep up healthier mentally and physically and perhaps even slow down dementia. A brother or sister may even be the one to look after us.

"The longer life expectancies get, the more of us will arrive in an old age in which we've outlived a spouse and other loved ones, and our kids have scattered," said Kluger. "Sibs are often the only ones left -- and often the people who know you and love you the best."

He continues close ties with his three brothers and two half-siblings through e-mail, regular phone calls and Skype.

"Another thing that struck me in a positive way was blended families," he said. "Six years is the threshold point past which step-siblings become virtually indistinguishable from whole siblings. In some ways, they are closer because they don't have early life competition."

But old rivalries can persist, even decades later, especially at family gatherings.

"Someone once said, 'When I go home for Thanksgiving, so often the meals turn into old family wars.' Of course, people push the buttons – they installed them," said Kluger.

As for Bruce, he was always his mother's favorite, "in part because he was my father's least favorite and came in for occasional harsh treatment as a result," remembers Kluger, who always felt "a bit in the shadow" of the bespectacled redhead with the "incandescent personality," even well into adulthood.

A decade ago while visiting their mother, Kluger and his Bruce unconsciously regressed to childhood behavior. "We were walking toward her car and we both picked up the pace," he said. "We were racing to get the front seat."

Both boys have retained a sense of humor about the hours Bruce spent latched in the cabinet in the basement. After Kluger's book came out, Bruce Photoshopped a plaque on an old picture of their house: "6026 Berkeley: Home of the Fuse Box."

"We saved his life," said Kluger, only half-kiddingly.