The Gracchi, 2nd century BC
Fraternal amity is not a condition necessarily associated with the Roman Empire in its latter days, though the Gracchus brothers do seem to have held each other in high regard. Both tribunes of the Republic and both possessed of "eloquence sufficient to make the less creditable plausible", as Plutarch has it, their campaign on behalf of Rome's down-trodden alienated the senatorial elite and led to their end. Tiberius was slain with a foot stool by a Senator with a gripe. His brother Gaius committed suicide on the point of his personal slave's sword.
Elizabeth I and Mary I, 16th century AD
Although the Middle Ages are packed with tales of political intrigue among families, few relationships were as difficult as that of Elizabeth I and Mary I. Alike in dignity, they were opposed in matters of the cloth. Mary failed to fully impose Catholicism on England and when Protestants rose against her, she suspected her sister's involvement and imprisoned her. "Much suspected of me, nothing proved can be," Elizabeth carved into the window frame of her prison. And she was right, nothing was proved and the crown was hers four years later.
John and Robert Kennedy, 1960s
Equal in intellect and sexual stamina, Robert and John Kennedy were a close political and fraternal pairing. They wrought a cultural and political renaissance at the top of American politics, as they sought to share both power and Marilyn Monroe, amicably. Though adept at dodging their respective wives, they could not dodge the assassin's bullet. Robert fell within five years of his brother.
Jimmy and Billy Carter, 1970s
Although Jimmy Carter's brother Billy was not a politician, he certainly had a political effect. Billy, who boasted that he could drink 20 to 25 beers, was a problem for his brother. President Carter was able to laugh off his brother's habit of urinating in public and holding press conferences on the forecourt of his petrol station, but had trouble explaining why his brother had accepted a $200,000 loan from the Libyan Government and had to register as an agent of a rogue nation. "I think I helped him as much as I hurt him", Billy commented. History does not relate President Carter's response.
Lech and Jaroslaw Kaczynski, 2006
The government of Poland became a family affair in 2006, when President Lech Kaczynski appointed his twin brother Jaroslaw as Prime Minister. Famous as child actors, they became more famous for their right wing nationalism. Like many a sibling politician, Lech met a tragic end: dying in a plane crash over the Russian city of Smolensk. Jaroslaw is poised to succeed Lech in the forthcoming elections.