(NEW YORK) -- Brotherly love -- and its accompanying intense rivalry -- is a topic close to Jeffrey 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."
Kluger and his three brothers propped each other up emotionally throughout the multiple divorces of their unstable parents. Their prescription drug-addicted mother was married twice, bringing two stepsisters into the mix. Their volatile father also 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 ABC News. "We pull together."
Kluger notes that siblings are the ones, of all relatives, who share the longest stretch of time on earth.
"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."
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.
Copyright 2011 ABC News Radio