The Gaius Caesar reference article from the English Wikipedia on 24-Apr-2004
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Gaius Caesar

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Two notable individuals of the Roman Empire were commonly called Gaius Caesar.

The first Gaius Caesar was the son of Agrippa and Julia, and the heir apparent to Augustus Caesar, but died in 4 AD.

The second was the emperor Gaius Julius Caesar Germanicus, better known as Caligula.