In 25 BC, Augustus’ only daughter Julia was married to her cousin (Octavia’s son and Augustus’ nephew), M. Claudius Marcellus (b. 42).  Marcus Agrippa officiated at the wedding as Augustus was absent.

Augustus was seriously ill during this time, and by this marriage, Augustus was clearly preparing for Marcellus to become his immediate successor, as Velleius wrote:

People thought that, if anything should happen to Caesar, Marcellus would be his successor in power, at the same time believing, however, that this would not fall to his lot without opposition from Marcus Agrippa. He was, we are told, a young man of noble qualities, cheerful in mind and disposition, and equal to the station for which he was being reared.

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