Liz, left, and Mary Cheney, daughters of then-Vice President Dick Cheney at the 2004 Republican National Convention in New York City. (Jeff Haynes/AFP/Getty Images)

Lisa Bonos is Outlook’s assistant editor.

When a sibling rivalry gets out of control, how does it get resolved? In the Bible and in Shakespeare, someone usually dies. In politics, Mom and Dad release a statement.

The recap: Liz Cheney, who is running for the U.S. Senate in Wyoming, told “Fox News Sunday” last weekend that she loves her sister, Mary Cheney, but that gay marriage is “just an issue in which we disagree.” Mary, who is married to her longtime partner, Heather Poe, shot back on Facebook that Liz is “on the wrong side of history.” Then Dick and Lynne weighed in, addressing a feud that reflects one within their party as well. “This is an issue we have dealt with privately for many years, and we are pained to see it become public,” they said. “Since it has, one thing should be clear. Liz has always believed in the traditional definition of marriage.”

Historically, siblings and politics haven’t always mixed well — whether they’re fighting over same-sex marriages or arranged ones:

A statue of Queen Isabella I in Toledo, Spain. She defied her brother’s plans for her to marry King Afonso of Portugal. (Denis Doyle/Associated Press)
15th century: Isabella and King Enrique

In 1468, King Enrique of Castile, what is now north-central Spain, wanted his teenage half­sister, Isabella, to marry Portugal’s King Afonso V. To Enrique, the marriage would be an insurance policy: “He faced a rebellion over his poor rulership and hoped to gain Portuguese military aid to defeat the rebels,” says Stephen Bown, author of “1494: How a Family Feud in Medieval Spain Divided the World in Half.”

But Isabella wasn’t having it: She found Afonso repulsive. (He was her uncle by marriage and more than twice her age, so that might have been a factor.) Though Enrique threatened to imprison Isabella for defying him, she escaped and married her second cousin, the young Prince Ferdinand of the neighboring kingdom of Aragon.

“The struggle to determine Isabella’s marriage partner was a major stumbling block for Castilian peace,” Bown writes. Even after Enrique’s death in 1474 and Isabella’s ascension to his throne, this battle over marriage freedom — namely a woman’s right to choose her husband — was far from over. Still stung by the botched nuptials, King Afonso invaded Castile, sparking a years-long war.

John Wilkes Booth, who assassinated President Abraham Lincoln, lived in his brother’s shadow and often fought with him over politics. (Associated Press)

Edwin Booth’s acting career was much more successful than that of his brother, John Wilkes Booth. (Associated Press)
1860s: Edwin and John Wilkes Booth

John Wilkes Booth’s name is etched in America’s memory for his assassination of Abraham Lincoln just five days after the end of the Civil War. But there was a more private battle that John Wilkes endured — a tense rivalry with his older brother, Edwin.

The siblings sparred on several fronts: They both were actors, trying to claim the legacy of their father’s famed stage career. But John Wilkes wasn’t nearly as talented or politically connected as Edwin, who garnered critical acclaim, owned a theater on Broadway, gave large sums to the Union war effort and socialized with officials in the Lincoln administration. And, like many Maryland families at the time, they were split over the Civil War, with Edwin accusing his brother of treason for siding with the Confederates. “In the privacy of Edwin’s townhouse in Manhattan, the brothers had shouting matches over Lincoln and the progress of the war,” writes Nora Titone, author of “My Thoughts Be Bloody: The Bitter Rivalry Between Edwin and John Wilkes Booth That Led to an American Tragedy .” “These arguments were so heated, they at times erupted in physical conflict.”

Union Army officer Adam Badeau, an aide to Gen. Ulysses S. Grant and a close friend of Edwin and John Wilkes, wrote that John’s crime “was exactly what a man brought up in a theater might have been expected to conceive.”

Former British foreign secretary David Miliband, right, lost an election to lead the Labor party to his younger brother, Ed. David rallied the party faithful at this 2010 event, declaring that “Ed’s a great leader.” (Christopher Furlong/Getty Images)
2010-2013: David and Ed Miliband

When asked to name the best example of a sibling rivalry in politics, congressional scholar Norman J. Ornstein points across the Atlantic to David and Ed Miliband.

Just a few years ago, David was a rising star in British politics. He was Tony Blair’s chief of policy at age 29. At 35, he was elected to Parliament and went on to serve in the cabinet as environmental secretary and foreign secretary. Then, in 2010, he narrowly lost an election to lead the Labor Party — to his younger brother, Ed.

Opting to leave Parliament rather than serve in his brother’s shadow cabinet, David told the BBC this March that “I didn’t want to become a distraction; I didn’t want the soap opera to take over the real substance of what needs to be done.”

Now there’s an ocean between them, and David has found another leadership position — as head of the International Rescue Committee in New York.

Oasis split up in 2009 after Liam Gallagher, left, and his older brother Noel had a falling-out. (Daniel Luna/Associated Press)

2009-present: Liam and Noel Gallagher

Okay, this one’s not political, but it’s a supernova of a spat.

It’s tough to tell what sparked the breakup of the Britpop band Oasis: It’s a lot of he-said, he-said, with a side of flying fruit.

Noel says the fight started when his younger brother, Liam, wanted to advertise his clothing label in the Oasis tour program, a move Noel opposed. Noel says Liam showed up late to a 2009 gig in Paris because he was hungover; Liam maintains that he had laryngitis and hadn’t asked for cross-promotion, and that Noel was “being rude to people who’d been working for us for 18 years.” Before that 2009 show, the brothers got into a physical fight in the dressing room.

As Noel tells it, Liam “picked up a plum and he threw it across the dressing room, and it smashed against the wall.” Next, Liam reportedly shattered a guitar , and Noel walked out, canceling the show and posting a note to fans saying, “It’s with some sadness and great relief to tell you that I quit Oasis tonight.”

Alex Niven, who’s writing a book about the band, thinks that the feud is “a classic big-brother/little-brother thing of Liam continually striving for Noel’s attention by winding him up, Noel getting annoyed and trying to ignore Liam, Liam getting annoyed at this in turn.” Niven adds: “Within the band this was exacerbated because Noel wrote the songs but Liam was the frontman, which essentially created an ongoing power struggle.”

Will they get back together? Paul Gallagher, the musicians’ older brother, has offered hope: “All it takes is two guys to say, ‘You know what, I’m sorry, but I love you.’ That’s all it takes, it’s not hard. It’s easy.”

It’s too late for Isabella and Enrique and Edwin and John Wilkes to reconcile — but not for David and Ed, Liam and Noel, Mary and Liz.

May we suggest “Don’t Look Back in Anger ” for the opening tune of a reunion tour?

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