In Paula Broadwell's biographer of former CIA director David Petraeus, she wrote that he and his wife, Holly, had a "virtually unbreakable marriage," in the words of the Daily Mail. 

Broadwell's book "All In: The Education of General David Petraeus," which included details from dozens of interviews between Holly and David, described how the couple met and fell in love, adding that their relationship was "virtually unbreakable," according to the news report. However, at the same time that Broadwell was doing research for her book, she started an extramarital affair with David without Holly's knowledge. 

Only last month, David and Holly celebrated the marriage of their daughter Anne in Berryville, Va., according to The Washington Post. Retired Gen. Jack Keane, who attended the wedding, said, "Holly and Dave were both beaming throughout their evening."

Holly and David met in 1973 when he was a cadet at the U.S. Military Academy at West Point and her father was the superintendent. They married in July 1974 at the West Point chapel. Holly admitted that as a military spouse, she moved with her husband 24 times in 37 years of marriage, according to the news report. Their son Stephen served in Afghanistan and Holly is the assistant director for the Obama administration's Consumer Financial Protection Bureau, monitoring and investigating complaints from U.S. service members. 

Discovery of the extramarital affair with Broadwell forced Petraeus to resign as CIA director on Friday. He and Broadwell got close as she did research for her biography. 

Petraeus told friends the affair began in August of 2011 after he left the army, according to ABC News. Broadwell is married and has two children and Petraeus and his wife have been married for 38 years and also have two children.  

The Uniform Code of Military Justice states that adultery is punishable under Article 134, with "a maximum punishment of dishonorable discharge, forfeiture of all pay and allowances and confinement for one year," according to The Huffington Post.