Her marriage to Germanicus had served to unite the imperial family. Agrippina may have suspected Tiberius' involvement in the death of her husband and, with Germanicus dead, she no longer had any familial ties to the emperor. Historian Richard Alston says it is likely that either Tiberius or Livia were behind the exile of Agrippina's half-sister and the death of Postumus. He notes the death of Agrippina's mother, who starved herself to death amidst her exile in AD 14, linking her death to Tiberius' disdain for her.