"I don’t understand why people take only one wife," Osama bin Laden would often say, in what was the nearest he ever came to a lighthearted quip. "If you take four wives, you live like a groom."

But Osama disapproved of how his own father, the wealthy Yemeni builder Mohammed bin Laden, went about the Islamic sanctioned practice of polygamy that allows a man to legally take up to four wives.

One of 54 children, Osama was born in 1957 to 15-year-old Allia Ghanem, one of at least 20 women whom Mohammed, nearly 40 years her senior, had married and divorced during his lifetime. Osama, their only child, was 3 years old when Mohammed cast his mother aside. Allia, her son said years later, was "not a wife of the Koran, but a concubine."

Rather than renounce polygamy, though, Osama bin Laden decided that his father had merely been doing it wrong.

"To be a true Muslim," bin Laden believed "you should only marry the four wives sanctioned by Islam and then … treat all four of them fairly," writes national security analyst and former CNN producer Peter Bergen in "The Rise and Fall of Osama bin Laden" (Simon & Schuster), out Tuesday.

UN COMPOUND IN ATTACKED, AT LEAST ONE GUARD KILLED

That, the fundamentalist believer claimed, was far superior to his father’s practice of churning through wives by constantly divorcing them and marrying new ones.

By the time he instigated the Sept. 11 attacks in 2001, bin Laden, then 44, was living in Afghanistan with three wives. The older two — Khairiah Sabar, 52, a devout child psychologist who had abandoned an established career to marry him, and Siham al-Sharif, 44, a poet who held a Ph.D. in Koranic grammar — edited his speeches, honed his religious declarations and encouraged his plans for global jihad.

Meanwhile, his third wife, Amal el-Sadah, a naive 17-year-old from rural Yemen, brought out his vanity.

"He drank Avena, a syrup made from oats that claims to have Viagra-like effects, and he ate copious amounts of olives, which he believed produced similar results," writes Bergen. "He also regularly applied Just for Men dye to his beard." 

In the immediate aftermath of 9/11, which killed 2,977 people, Osama’s extended family scattered to the wind. Meanwhile, the jihadist who founded Al Qaeda to wage holy war on the West concealed himself in the Afghan mountains and in northern Pakistan to evade justice. But by 2004, as the United States bogged itself down in nation-building efforts in Afghanistan and Iraq, bin Laden felt the heat of the chase dissipate. 

That’s when the world’s most wanted man ordered his bodyguard, Ibrahim Saeed Ahmed abd al-Hamid, to buy some land, hire an architect, and build a fortress big enough to house the family he was intent on reuniting in Abbottabad, Pakistan. 

Ibrahim went to work, putting the $50,000 real-estate purchase in his own name and designing a home to his boss’ specifications. The three-story main house had four bedrooms on the first floor and four more on the second, each with its own bathroom. The top floor contained a bedroom, bathroom, study and terrace for bin Laden’s use. In 2005, family members began moving in.

Ibrahim, who ostensibly owned the property, his brother, Abrar, and their wives and children regularly came and went. But they resided in a small annex, not in the main building. 

The brothers followed strict operational security measures to keep a low profile. They used public phone booths in large cities to make important calls and took the batteries out of their cellphones so they couldn’t be tracked to their home base. 

Usama bin Laden speaks in this undated image taken from video provided by the U.S. Department of Defense.

Usama bin Laden speaks in this undated image taken from video provided by the U.S. Department of Defense. (AP)

AFGHAN TRANSLATOR WHO WORKED FOR US ARMY REPORTEDLY BEHEADED BY TALIBAN

The bin Ladens rarely if ever left the compound — except for Amal, who had gone twice to a local hospital to give birth under an assumed name, showing fake identification papers and feigning deafness to avoid awkward questions. 

But in 2010, the CIA got a break: A Pakistani informant in the crowded city of Peshawar spotted a man believed to be Ibrahim, bin Laden’s longtime bodyguard. 

In August 2010, Ibrahim’s white Jeep led the CIA to the property’s 18-foot-high, barbed-wire-topped walls. The place was packed with bin Laden’s three wives, eight of his youngest children, and four grandchildren, including 2- and 3-year-old babies. 

The property had many unusual features that made CIA analysts take note. It had no telephone lines or Internet service — despite the fact that whoever built it was surely wealthy enough to afford such necessities. The large main house had few windows, and the top floor’s open-air balcony was surrounded on all sides by a high wall. 

"Who puts a privacy wall around a patio?" then-CIA Director Leon Panetta asked his staffers. 

"Exactly," one analyst replied. 

The agency set up a safe house near the mysterious compound to perform a "pattern of life" study on whoever was living there. 

While neighbors put their trash out for regular garbage pickups, the compound dwellers burned all their refuse. 

The acre of land enclosed within the walls contained a small farm that produced apples, vegetables, grapes, and honey and housed chickens and even cows — food that was apparently being consumed by unseen residents. 

But the final clue was the clotheslines on the compound, which flapped each day with women’s garments, shalwar kameez worn by Pakistani men, children’s outfits and diapers — far more than the 11 members of the bodyguards’ families could ever wear. 

The invisible inhabitants, according to the agents’ laundry calculations, had to include an adult man, several adult women, and at least nine children, a perfect fit for the polygamous patriarch they were seeking. 

After more than nine years in hiding, Osama bin Laden was betrayed by his family’s laundry. 

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That was enough for Panetta. On Dec. 14, 2010, he presented the CIA’s evidence to then-President Barack Obama. 

Agents never managed to capture a clearly identifiable image of bin Laden to prove they had finally uncovered his hiding place. But "they also never found evidence that undercut the notion that he was living there," Bergen writes. 

Obama was convinced. He ordered the Navy to begin planning the operation that would ultimately, on May 1, 2011, snuff out the terror master at age 54 — a decision that might never have been made if bin Laden had thought to give his wives a clothes dryer.

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