Oh, brother

Tomorrow, the Duke of SussexThe official title of Prince Harry. publishes his memoir: Spare. The title refers to the traditional practice where the eldest son inherits everything from his parents. The younger brother is just a "reserve king".

This fraternalBrotherly. relationship can lead to jealousy and bitterness. For the princes, it became a public row. But in history, sibling rivalry has led to blood, war and the fall of empires.

The first murder. In the Bible, Adam and Eve's eldest son Cain grew jealous of his younger brother Abel. God accepted a sacrifice from Abel but refused Cain's gift. In a fury, Cain killed Abel.

Death in Rome. The origin myth of the Roman Empire has a dark twist. Twin brothers Romulus and Remus fought over where to build Rome. When Remus ignored an omenAn event seen as a sign that something good or bad is about to happen. from the gods, he was killed.

Romans thought this myth stressed the importance of unity and obeying the gods.

Divided spoils. According to one chronicler¹, William the Conqueror's three sons fell out over a prank. William Rufus and Henry tipped a chamber pot over Robert's head. He never forgave them.

When William I died, he split his kingdom between them, sparking a civil war. William Rufus was killed in a suspicious hunting accident.² Henry threw Robert in prison and ruled for 35 years until he ate a plate of poisoned eels.

Brothers in arms. During the Wars of the RosesA series of civil wars that took place between between 1455 and 1485. Two competing royal houses, the House of York and the House of Lancaster, fought for the English throne. , the rivalry between three brothers tore apart the House of York.

Historians disagree about who killed who. But Shakespeare made the youngest into the story's villain. In his play³, Richard III drowns his brother George in a barrel of wine and murders Edward's sons in the Tower.

Culture clash. In 1532, 169 Spanish soldiers invaded the Inca Empire. The IncasA native South American people who lived in the Andes before the Spanish conquest. had enormous and powerful armies. But they were also divided by a bloody civil war between two brothers, Atahualpa and Huascar.

The Spanish took Huascar's side in the conflict. After Atahualpa killed his brother, the Spanish executed him and took control.

The psychologist Alfred Adler argued that siblings compete for "significance". It is the fundamental rivalry that shapes our world.

But others argue brotherly love holds society together. Fraternity underpins many religions and political movements.

Yes: History is the story of men dividing their land and wealth between their sons. No heir was a problem. One son secured the family's future. Two or more meant trouble.

No: There is so much more to history. For example, better technology helped the Spanish defeat the Incas. And new diseases from Europe killed more people than the Spanish.

Or... Sometimes. "The heir and the spare" survives in the British royal family, but the rest of society has changed. Power and positions are no longer inherited but given based on ability and merit.