It has been assumed by Ronald Syme, [1] among others,[2] that her mother was Julia Livia (daughter of Drusus Julius Caesar and Livilla), which would make Bassa the great-granddaughter of Tiberius and the great-great-niece of Augustus through his sister Octavia the Younger.
[citation needed] It has been argued that the motivation for Blandus and Julia's marriage was because Tiberius wanted a mature husband for his granddaughter who had little political ambition, and thus posed no threat to the position of his designated heir, Tiberius Gemellus.
[1] Bassa had at least one full sibling or half-sibling, a brother named Gaius Rubellius Plautus who was one of the nearest heirs of the blood of Tiberius, being the grandson of Drusus Julius Caesar.
[3] Rubellia Bassa married Gaius Octavius Laenas, a maternal uncle of the future emperor Nerva.
Syme notes that Sergius Octavius Laenas Pontianus, consul in 131 under Emperor Hadrian, set up a dedication to his grandmother, "[Rub]elliae / [Bla]ndi f(iliae) Bassae / Octavi Laenatis / Sergius Octavius / Laenas Pontianus / aviae optimae ".