Augustus realized that should he himself die, the two young boys would be left without a guardian.
Alas, Augustus turned to his wife Livia's two adult sons from her previous marriage. He made the elder son, Tiberius, divorce his wife Vipsania and marry Julia, and become protector to the young princes.
Tiberius deeply loved his wife Vipsania and strongly resented Augustus' demands, but the marriage went ahead on 12 February 11 BC.
As both Gaius and Lucius died early in their lives, Augustus was left with only one choice of successor - Tiberius, son of Livia. And so, on 26 June AD 4 he somewhat reluctantly adopted the equally reluctant 44 year old Tiberius, together with the 15 year old Agrippa Postumus, the youngest son of Agrippa and Julia.
Postumus though soon turned out to be a violent and nasty person and so was sent into exile only three years later. During his final years Augustus withdrew more and more from public life. Intending to travel with Tiberius to Capri, and then on to Beneventum, he left Rome for the last time in AD 14.
He fell ill on the way to Capri and, after four days resting on Capri, when they crossed back to the mainland Augustus alas passed away. He died at Nola on 19 August AD 14, only one month away of his 76th birthday.
The body was taken to Rome and given a stately funeral and his ashes were then placed in his Mausoleum.