Ptolemy succeeded in 180 at the age of about 12 and ruled jointly with his mother, Cleopatra I, until her death in 176 BC. The following year he married his sister, Cleopatra II.
In 170 BC, Antiochus IV began the sixth Syrian War and invaded Egypt twice. He was crowned as its king in 168, but abandoned his claim on the orders of the Roman Senate. From 169-164 Egypt was ruled by a triumvirate consisting of Ptolemy, his sister-queen and his younger brother known as Ptolemy VIII, but in 164 he was driven out by his brother and went to Rome to seek support, which he received from Cato. He was restored the following year by the intervention of the Alexandrians and ruled uneasily, cruelly suppressing frequent rebellions, until he was killed in Syria, fighting against Alexander Balas.
PTOLEMY V. Epiphanes reigned 204-181), son of Philopator and Arsinoe, was not more than five years old when he came to the throne, and under a series of regents the kingdom was paralysed.
But in 147 Philometor broke with him and transferred his support, together with the person of Cleopatra, to Demetrius II., the young son of Demetrius I. He himself at Antioch was entreated by the people to assume the Seleucid diadem, but he declined and installed Demetrius as king.
Philometor's infant son, Ptolemy Philopator Neos (?) 1, was proclaimed king in Alexandria under the regency of his mother Cleopatra.