For Omar bin Laden, the fourth eldest of Osama bin Laden's 20 known children, the awful realization that his father was a terrorist mastermind who was plotting a global conspiracy that would destroy the lives of thousands of innocent people and even his own family came gradually. Of course, there were warning signs: Omar's childhood was marked by regular beatings and survivalist training; the growing army of ruffians and retainers who called his father "Prince"; and that Afghan mullah who had given his father an entire mountain in Tora Bora.But as he recounts in a book co-written with his mother, Omar — now 28 years old — found it hard to give up hope that a man who had killed so many people might one day turn his back on violence and become a normal father. The younger bin Laden fled Afghanistan only when it become clear that Osama was planning a massive attack on the U.S., but he still couldn't accept that his father was responsible for 9/11 until months later, when he heard the familiar voice on audiotape claiming credit for the attacks. "That was the moment to set aside the dream I had indulged, feverishly hoping the world was wrong and it was not my father who brought about that horrible day," he writes. "This knowledge drives me into the blackest hole."As the first book written about Osama bin Laden with help from anyone in the bin Laden family, Growing Up bin Laden: Osama's Wife and Son Take Us Inside Their Secret World (St. Martin's Press) is a valuable — if limited — glimpse into the personal life of the world's most wanted man. In recollections from Omar and his mother Najwa bin Laden (the first of Osama's five known wives), and with the assistance of American author Jean Sasson, the book paints a picture of Osama as a towering figure whose noble demeanor inspired fierce loyalty, but also an absolute authoritarian who wanted as many wives and children as possible in order to have foot soldiers for Islamic jihad. "My sons, your limbs must react to my thinking as though my brain was in your head," he told his children when they complained about their life in al-Qaeda camps.However, Osama the father remains almost as elusive to his son (and the reader) as he is to the FBI — too consumed by jihad to care much for his children, too distant to seem like a full person. But Omar's memoir — which forms the core of the book — presents a strange and fascinating coming-of-age-story about a young boy who was groomed by his father to take over a worldwide terrorist enterprise but who instead chooses to get a job, start a family and play with animals. If the book suffers somewhat from the limitations of translation and overly formal prose, the thrill of being a fly on the wall of the bin Laden family drama quickly takes over.Omar's early childhood is both charmed and abusive. Though the family inhabited a mansion in the Saudi city of Jeddah and owned horse ranches in the desert, their father refused to let them have toys, take modern medicine or use almost any modern conveniences except for lightbulbs, automobiles and firearms. Though Osama would punish his boys for laughing or smiling and send them on forced marches in the desert without water, Omar and his brothers could at least console themselves with the honor of being sons of the man who helped defeat the Soviet Union in Afghanistan, a hero in both the Muslim world and the West. "When I was a young boy, I worshipped my father, whom I believed to be not only the most brilliant, but also the tallest man in the world," Omar writes. "I would have to go to Afghanistan to meet a man taller than my father. In truth, I would have to go to Afghanistan to truly come to know my father."The nightmare began in earnest after the Saudi government banished Osama from the kingdom for railing against Riyadh's decision to allow American soldiers on Saudi soil to repel Saddam Hussein's invasion of Kuwait. From the new family home in Sudan, while Osama plotted to overthrow the Saudi monarchy and the American government, Omar noticed some dangerous new arrivals in their Khartoum neighborhood, including Ayman al-Zawahiri, the leader of an Egyptian Islamist movement who would become al-Qaeda's second-in-command. When members of another extremist group raped one of Omar's male friends, al-Zawahiri took justice into his own hands — by executing the victim.Step by step, Omar found himself stuck on the violent path of his father's choosing. Forced by American pressure to leave Sudan for Afghanistan, Osama settled his family in stone huts high on a mountain in Tora Bora, despite the fact that Najwa was pregnant with her 10th child. Osama sent his sons to al-Qaeda training camps, to the front lines of the Afghan civil war and to attend hours of mind-numbing jihadist indoctrination. Omar and his father narrowly survived a U.S. cruise-missile strike that was launched in retaliation for the al-Qaeda bomb attacks on two U.S. embassies in Africa. All the while Osama expected Omar to become his second-in-command. The young man had somehow managed to develop into a serious, capable young adult even as many of his siblings appeared to have suffered from one kind or another of personality disorder related to their extreme upbringing. One day while sitting together on the bin Laden mountain, Osama revealed to Omar his plan to destroy the U.S. from within by making it bleed through constant war until Muslims ruled the world. But Omar wasn't interested. "I sat mute, feeling not one jolt of passion for my father's life," he writes. "I only wanted him to be like other fathers, concerned with his work and his family."(See pictures from a jihadi's scrapbook.)Still, ever the dutiful Saudi son, Omar couldn't bring himself to break with his family until the day that his father asked his sons to volunteer for suicide missions. When Omar protested, Osama replied, "You hold no more a place in my heart than any man or boy in the entire country. This is true for all my sons." Omar writes, "I finally knew exactly where I stood. My father hated his enemies more than he loved his sons." With rumors of a massive attack on bin Laden's enemies on the way, Omar finally managed to leave Afghanistan, with his father's permission.After the carnage of 9/11, there was no going back. Many of Omar's siblings who stayed behind are probably dead, and his father is the most famous mass murderer alive today. "During these years of loss and sorrow, I have had to reconcile myself to the truth about my father," writes Omar. "I know now that since the first day of the first battle against the Soviets in Afghanistan, my father has been killing other humans. I often wonder if my father has killed so many times that the act of killing no longer brings him pleasure or pain. I am nothing like my father. While he prays for war, I pray for peace."(Read "Eight Years After 9/11: Why Osama bin Laden Failed.")In an interview with TIME, Omar said that as a private citizen working for the construction company owned by his father's estranged family, he had little insight on how the U.S. should fight al-Qaeda. He turned down a U.S. government offer of asylum for cooperation in finding his father. "I said you — the CIA and the FBI — you should know where he is, but I can't help you because I don't," Omar said by phone from a Middle Eastern country he refused to name either for fear of his safety or residency status. He has technically been reinstated as a Saudi subject.Intelligence agencies and scholars of extremist movements might do well to pay attention to Omar's al-Qaeda childhood for clues about how to inoculate young people against radicalism. His remarkable achievement — to have maintained humane beliefs despite being pulled from school at the age of 12 and exposed to a near constant deluge of hateful propaganda, isolation and family pressure — seems to have been helped by a love of animals. A constant collector of pets — against his father's wishes — and an avid horseman, Omar's awareness of the madness of al-Qaeda was fueled in part by several acts of animal cruelty by his father's men. When they lived in Sudan, one of the family guards killed Omar's pet monkey by running it over with a truck, explaining that the creature was in fact a Jew turned into a monkey by the hand of God. Later, Omar learned that it was his father who taught the guard that monkeys were Jews.Now an adult and free from his father, Omar talks about starting a worldwide peace movement. But having spent much of his life in the wilds of Afghanistan, his ideas about how the world works are hazy. The U.S. government is unlikely to start a dialogue with Osama bin Laden, as he suggests. Another idea, a horse race across North Africa, seems more appropriate. Perhaps a world where people are kinder to animals will be one where they are kinder to one another.