- Nero Cladious DRUSUS
DEATH: Also shown as Died 0009
SURNAME: Also shown as Nero
GIVEN_NAMES: Also shown as Drusus Claudius
BIRTH: Also shown as Born 0038 BC
DEATH: Also shown as Died 0009 BC
Nero Claudius Drusus Germanicus, born Decimus Claudius Drusus and variously called Drusus, Drusus I, Drusus Claudius Nero, or Drusus the Elder (14 January 38 - 9 BC) was the youngest son of Livia, wife of Augustus, and her first husband, Tiberius Claudius Nero, and was thus a patrician Claudian on both sides.
Drusus was born shortly before Livia divorced Tiberius Claudius Nero and married Augustus (17 January, 38 BC), giving rise to rumors that Augustus was the real father, although this is widely discredited by modern historians as Augustus had not yet met Livia when Drusus would have been conceived. Before Augustus married Livia, Tiberius Claudius Nero was declared Drusus' biological father. According to Suetonius, he was born with the praenomen Decimus, but it was later changed to Nero. He was raised in Claudius Nero's house with his brother, the future emperor Tiberius, until his father's death. Drusus and Tiberius developed a famously close relationship in this environment that would last the rest of their lives. Tiberius named his eldest son after his brother (in violation of Roman naming standards), and Drusus did likewise.
Drusus married Antonia Minor, the daughter of Mark Antony and Augustus's sister, Octavia Minor, and gained a reputation of being completely faithful to her. Their children were Germanicus, Livilla, the future Emperor Claudius, and at least two others who did not survive infancy. After Drusus' death, Antonia never remarried, though she outlived him by nearly 5 decades.
Augustus bestowed many honors on his step-sons. In 19 BC, Drusus was granted the ability to hold all public offices 5 years before the minimum age. When Tiberius left Italy during his term as praetor in 16 BC, Drusus legislated in his place. He became quaestor the following year, fighting against Raetian bandits in the alps. Drusus repelled them, gaining honors, but was unable to smash their forces, and required reinforcement from Tiberius. The brothers easily defeated the local Alpine tribes. In 13 BC, Drusus was sent to govern Gaul to quell riots caused by the actions of a previous administrator. While there, a tribe of Germans entered Gaul and proceeded to attack Roman settlements. Drusus mobilized his legions and beat the invaders back across the Rhine. He penetrated deep into German territory, traveling as far as the North Sea and placing a yearly tribute on the Frisians. As a reward, Drusus was made praetor urbanus for 11 BC.
Drusus did not have it in him to stay in Rome. In the spring of his term, he set out for the German border once more. He pushed once more into the territory of the various German tribes, only stopping at the onset of winter. He was attacked while making his way back to Roman territory, but managed to rout the German force. His troops proclaimed him Imperator and he was granted triumphal ornaments, as well as the office of proconsul for the following year. In 10 BC, the Chatti joined with the Sicambri and attacked Drusus' camp, but were easily defeated. Drusus then went to meet Augustus and Tiberius in Lugdunum (at which point Claudius was born), and traveled with them to Rome. He was easily elected Consul for 9 BC, but once more left the city before assuming office. He once again smashed the Chatti, and then began a campaign against the Marcomanni, but was turned back across the Rhine. Drusus died soon after in consequence of a fall from a horse, lingering on for a month after the accident, by which point Tiberius had joined him. Suetonius reports that he had refused to return to Rome just before his death. Drusus' body was brought back to the city, and his ashes were deposited in the "Mausoleum of Augustus." He remained extremely popular with the legionaries, who erected a monument in Moguntiacum (modern Mainz) on his behalf. His family was granted the hereditary honorific "Germanicus", which was given to his eldest son before passing to his youngest. Augustus later wrote a biography of him which did not survive.
 Evidence that Augustus was the biological father of Drusus
Augustus was infamous for being chronically "sickly" (although he lived to be 75), and records of the symptoms he suffered from match those of Wilson's disease, an autosomal recessive genetic disease.
Tiberius was already 4 when Augustus married Livia, while she supposedly was already pregnant with Drusus. Drusus' son was Germanicus, and Germanicus married Agrippina the Elder. Their son was Caligula. Caligula, often called "the Mad Emperor", was affected by more severe symptoms that match with Wilson's disease; apart from the intestinal problems and immune system weakness of Augustus, he was mentally unstable and suffered from psychosis.
Because Wilson's disease is recessive autosomal, each of his parents would have to have been a latent carrier for the disease. It is entirely possible that Agrippina inherited the allele for Wilson's disease from her grandfather Augustus, but the only way Caligula could have Wilson's disease is if his father Germanicus was also a carrier. As it is a rare disease, it is unlikely that Germanicus inherited it from his normal-type mother. Thus Germanicus had to have been given the allele by Drusus, and the only way that Drusus could have the allele for Wilson's disease is if he got it from his biological parent: Augustus. This linkage shows that Augustus was Drusus' biological father.
Nero also probably suffered from Wilson's disease, and he was the son of Caligula's sister Agrippina the Younger and Gnaeus Domitius Ahenobarbus. Claudius, brother of Germanicus, probably also suffered symptoms of Wilson's disease, lending further proof to the genetic mapping. (Compare this pedigree to that of, say, the presence of the hemophilia gene in the monarchs of Europe descended from Queen Victoria).
Evidence that Augustus was not the biological father of Drusus
Augustus never acknowledged Drusus as his son, he didn't even adopt him. He believed he only had one known biological child, Julia the Elder, his daughter by Scribonia. She gave birth to the five grandchildren (3 boys, 2 girls), whom he adopted as his heirs. After the deaths of 2 of his grandsons by Julia, and the banishment of the third, Augustus never moved to adopt Drusus' sons, Germanicus and Claudius. They were nearly the same age as Julia's sons (Germanicus was older than Postumus), and would have been his illegitimate grandsons if he were Drusus' father. Instead Augustus chose the much older Tiberius, who was definitely not related by blood, as sole heir and invested him with the powers of principate. Augustus seems to have had Tiberius adopt Germanicus as heir because of the latter's marriage to his granddaughter Agrippina (the last of Augustus' living grandchildren not in disgrace), and not because of any secret blood relationship.
Augustus and Livia were married for 51 years and both young when they married. Augustus was 25 and Livia was 19 but they never had children after their marriage. It may have been that Augustus and Livia were incapable of having their own children together. They had both successfully had children with other people (Augustus had Julia with Scribonia and Livia had Tiberius and Drusus with their father) but not with each other.