Usually it was not only the family fortune that was passed on from father to son in aristocratic families in ancient Rome; sons also inherited the close relationships within the aristocratic society, alliances known as “friendships,” as well as any political prestige that the father had enjoyed with the people of Rome and the soldiers of the Empire. If the emperor had a son or had adopted one, that son was thus automatically destined to be the successor. Women, especially wives or daughters of an emperor, could also play a crucial role in the question of succession if they had a son from a previous marriage or had given birth to a grandson of the emperor. As a result family relationships acquired great political significance, which could destabilize the position of a reigning emperor as well as support it.

Although Augustus had no son of his own, he did have a daughter, Julia, from a former marriage. His second wife, Livia, for her part had brought two sons with her into the marriage: Tiberius, the later emperor, and Drusus (known as Drusus I, or Drusus the Elder). Augustus chose to signal and secure his choice by arranging for the presumptive successor to marry Julia: first his nephew Marcellus and then, after Marcellus’s early demise, his chief general and associate, Marcus Agrippa. When Agrippa also died in 12 B.C. Augustus adopted his two grandsons from Julia and Agrippa’s marriage, Gaius and Lucius, who thus became candidates for the throne. Both of them also predeceased Augustus, however, so that the choice finally fell on his stepson Tiberius. He, too, had to marry Julia, and of all the candidates was the one who actually lived to become her father’s successor.