Berenice III reigns over Egypt for about a year.

Ptolemy XI Alexander, who had been carried off to Rome, had been befriended by Sulla; he is now sent to Egypt to be married to his Berenice, who is his stepmother.

Neither the queen nor the people of Alexandria, who greatly admire her, have been consulted about the matter.

When Ptolemy realizes, after about nineteen days of joint rule, that Berenice is loath to surrender her accustomed authority, he unwisely arranges for the murder of the popular queen, for which the enraged Alexandrians kill him in revenge, thus eliminating the last fully legitimate member of the Ptolemaic dynasty.

As Ptolemy XI has died without a male heir, the only available male descendants of the Ptolemy I lineage are the illegitimate sons of Ptolemy IX by an unknown Greek concubine.

The boys had been living in exile in Sinope, at the court of Mithridates VI, King of Pontus.

As the eldest of the boys, Ptolemy XII is proclaimed king as Ptolemy XII Neos Dionysos and marries his sister, Tryphaena.

However, Ptolemy XI had left the throne to Rome in his will, therefore Ptolemy XII is not the legitimate successor.

Nevertheless, Rome does not challenge the succession of Ptolemy XII because the Senate is unwilling to acquire an Egyptian expansion.

His precarious kingship depends heavily on Roman support.