Ovid's Fasti as indicating a date of 13 January. Rumors arose that Augustus was the child's real father, although impossible as Livia was already pregnant when she met her future husband, (Emperor Claudius nonetheless encouraged the rumor during his reign to create an impression of more direct lineage from Augustus). Drusus was raised in Claudius Nero's house with his brother, the future emperor Tiberius, until his legal father's death. The two brothers developed a famously close relationship that would last the rest of their lives. Tiberius named his eldest son after his brother, although eldest sons were usually named after their father or grandfather. Drusus named his second son (future emperor Claudius) after Tiberius. Name According to Suetonius, Drusus was originally given the name Decimus Claudius Drusus but it was later changed to Nero Claudius Drusus. It is not known when or why the change occurred. The names were unusual at the time, both putting heavy emphasis on his maternal ancestry by using Livia's father's cognomen instead of that of her husband; in his original name the use of the praenomen Decimus was also atypical for prevalent families of the late Republic; the eventual use of his father's cognomen Nero as a praenomen was highly unconventional as well. Livia may have passed down her fathers cognomendn to her son simply because besides her adoptive brother Marcus Livius Drusus Libo there was no one else to pass it down for the future. C. J. Simpson asserted that there are three moments in history where the name change is probable to have happened; when his brother Tiberius was adopted by Marcus Gallius, when their father died in 33 BC, or when he assumed the toga virilis. Simpson personally argued against the time of adoption of his brother as a plausible time for his name change since Simpson believed the event may even have happened before Drusus was born, he also rejected the point of death of their father as likely since it would have probably have brought attention to the circumstances surrounding Livia's divorce and remarriage which had become a part of Mark Antony's propaganda at the time. Simpson stated that in his opinion Livia chose the names Decimus and Drusus for her younger son to minimize association with her ex-husband after she married Octavian due to the former's poor status at the time, but that several years after the man's death