Britannicus
Tiberius Claudius Caesar Britannicus (12 February AD 41 — 11 February AD 55) was the son of the Roman emperor Claudius and his third wife Valeria Messalina. He became the heir-designate of the empire at his birth, less than a month into his father's reign. He was still a young boy at the time of his mother's downfall and Claudius' marriage to Agrippina the Younger. This allowed Agrippina's older son Nero to eclipse him in the public's mind. He lived only months into his step brother Nero's reign, murdered just before his 14th birthday.
Read more about Britannicus: Birth and Early Childhood, The Fall of His Mother, Messalina, The Rise of His Step Brother, Nero, The Death of His Father, Claudius, The End of His Life, In Popular Culture, Ancestry