Incest of unequal gravity: the "incestus iuris gentium," which was applied to both Romans and non-Romans in the Empire, and the "incestus iuris civilis," which concerned only Roman citizens. Therefore, for example, an Egyptian could marry an aunt, but a Roman could not. Despite the act of incest being unacceptable within the Roman Empire, Roman Emperor Caligula is rumored to have had sexual relationships with all three of his sisters (Julia Livilla, Drusilla, and Agrippina the Younger). Emperor Claudius, after executing his previous wife, married his brother's daughter Agrippina the Younger, and changed the law to allow an otherwise illegal union.
Vipsania Agrippina Vipsania Agrippina Vipsania Agrippina (; 36 BC – 20 AD) was the first wife of the Emperor Tiberius. She was the daughter of Marcus Vipsanius Agrippa and Pomponia Caecilia Attica, granddaughter of Titus Pomponius Atticus. By marriage, she was a great-niece to Quintus Tullius Cicero. She was betrothed by Augustus and her father to Tiberius, the stepson of Augustus, before her first birthday. They were married around 19 BC. Their son Drusus Julius Caesar was born in 14 BC. Her father died in March 12 BC while married to his third wife Julia the Elder, the daughter of Augustus. Augustus