Cain versus Abel; Romulus versus Remus; Peyton versus Eli: History has experienced every shade of sibling rivalry, from frivolous to fatal. Here are nine particularly juicy ones sure to raise your eyebrows. Trust us. We guarantee it.

1. Cleopatra versus Ptolemy XIII

Before his death, Egypt’s King Ptolemy XII willed that his son, Ptolemy XIII, and daughter, Cleopatra VII, would succeed him as co-rulers. But things didn’t quite turn out that way. Frightened by her palpable ambition, Ptolemy XIII banished his sister in 49 BCE. Cleopatra responded by winning over one Julius Caesar, with whom she formed an alliance which ousted Ptolemy XIII for good. He drowned in the Nile while fighting to regain the throne.

2. Henry I versus Robert Curthose

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Despite being William the Conqueror’s eldest son, Robert never secured daddy’s crown. While he was busy fighting in the First Crusade, his father and his oldest sibling, William II, passed away. Command was therefore left to Henry, Robert’s younger brother. These two later clashed in the 1106 Battle of Tinchebray which saw Henry victorious and Robert imprisoned.

3. Elizabeth I versus Mary I

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Upon being crowned in 1553, the devoutly-Catholic Queen Mary I began working to divorce England from its Protestant infrastructure, something her half-sister, Elizabeth I, didn’t care for. After a short-lived rebellion against Mary was subsequently squashed, she accused Elizabeth of aiding its ringleaders and sentenced her to eight weeks locked inside the Tower of London.

4. Carcalla versus Geta

By now, it should be obvious that asking royals to share power is a dangerous game. Case in point: When the Roman emperor Septimus Severus named his sons Carcalla and Geta joint successors, he all but guaranteed a showdown between them. Sure enough, Carcalla eventually ordered his men to ambush and assassinate Geta, who died in their mother’s arms.

5. Cleopatra versus Arsinoe

Arsinoe was Cleopatra’s younger half-sister. That fact alone was cause enough for the female pharaoh to see this luckless woman as a threat and arrange for her execution (with a little help from the love-struck Mark Antony).

6. Artaxerxes II versus Cyrus the Younger

Shortly after Artaxerxes became king of Persia in 404 BCE, an advisor warned that his brother Cyrus was already planning to eliminate him. Sure enough, Cyrus amassed roughly 30,000 men and launched a full-on assault against Artaxerxes. Amazingly, in the heat of their definitive battle (one that involved some 90,000 combatants), these guys actually met face-to-face. Cyrus wound up injuring the king with his spear, but sustained multiple dart wounds and died later that day.

7. King Richard versus Prince John

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Robin Hood immortalized this spat. To make a long story short, Richard was captured and held for ransom in Germany after serving in the Crusades, which enabled his brother, John, to usurp the throne. Upon returning, Richard retaliated by confiscating the lion’s share of John’s land, but, having done so, forgave him “for being a child” who’d merely been “led astray by evil advisers.”

8. Al-Walid versus Sulayman

At its height, the mighty Umayyad caliphate stood as one of history’s largest empires, stretching from Spain to modern-day Iran. And, in 705, Al-Walid became its head honcho. But this came with a caveat he wasn’t particularly crazy about: that his brother, Sulayman, would rightfully assume the role of Caliph after his death. So, Al-Walid launched a campaign to have that torch passed to his son, ‘Abd al-‘Aziz, instead. Big mistake! Al-Walid’s efforts backfired tremendously and, as Caliph, Sulayman wound up enacting harsh vengeance upon all those who’d supported his brother’s child.

9. John Wilkes Booth versus Edwin Booth

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Though Edwin and John were both thespians by trade, the former rapidly upstaged his little bro and established himself as one of America’s favorite actors. Meanwhile, John was constantly slapped with bad reviews. Rather than being supportive, Edwin forbade his sibling from taking part in profitable Northern productions. A resentful John moved south, where his extreme secessionism began emerging. The rest, as they say, is history.