U.S. Army Lt. Stephen Petraeus looks into a box for suspicious items during a search. (Pfc. Donald Watkins/ AP)

It was one of those typical congressional hearings — point and counterpoint— until Gen. David Petraeus revealed a closely guarded secret last week: His only son, Stephen, had recently returned from combat duty in Afghanistan.

Like so many high-profile parents before him — Joe Biden, John McCain, Sarah Palin, Jim Webb — Petraeus kept the news of his son’s service under wraps. It finally went public Wednesday during a hearing with the House Armed Services Committee when he was pressed by Rep. Walter Jones on the exit date of American troops from Afghanistan: “For God sakes, how much more can we take, how much more can we give treasure and blood?” That’s when the the general shared his personal stake in the mission: “Lieutenant Petraeus just completed a tour in Afghanistan, which thankfully we were able to keep very quiet.”

“Very quiet” is the key here. Britain’s Prince Harry deployed briefly in 2008, thanks to an extraordinary deal with the media to keep silent but was forced to cut his tour short when the news leaked out. There were headlines when Track Palin, Beau Biden and Jimmy McCain went overseas and returned home, but very few details of their work. During his presidential campaign, Sen. McCain refused to discuss his son and even tried to kill a New York Times story that mentioned him.

Delaware Attorney General Beau Biden with other members of his Delaware Army National Guard unit at his deployment ceremony in 2008. (Rob Carr/AP)

Sen. Jim Webb famously wore his son Jimmy’s old combat boots during his campaign, but seldom talked about him — even with the president. Shortly after he was elected in 2006, Webb had a run-in with George W. Bush. “How’s your boy? Bush asked Webb. “I’d like to get them out of Iraq, Mr. President,” Webb answered “That’s not what I asked you,” Bush said. “How’s your boy?” Webb snapped back, “That’s between me and my boy, Mr. President.” (They later made peace, and the senator and his son met with Bush two years later.)

The Pentagon says these soldiers don’t want or get special treatment or cushy desk jobs; they just want to serve alongside their unit, even when their buddies recognize their famous name. (There are only two guys named “Petraeus” in the Army.)

But at least one VIP parent managed a special perk: The vice president was able to see his son three times during the year he served overseas. “I’ve found myself feeling somewhat guilty going back to Iraq as often as I did,” Biden said when the troops returned home in 2009. “I want you to know, for the press here, I was not doing it just to go see this unit. The president asked me to oversee Iraqi policy once we were elected.”