[8] His father Lysimachus was one of the Diadochi of Alexander the Great who was King of Thrace, Asia Minor and Macedonia.
Ptolemy I was another of the Diadochi of Alexander the Great who later founded the Ptolemaic dynasty of Ancient Egypt and Berenice I was the great-niece of the powerful Regent Antipater.
After the death of his half-brother, Agathocles’ cousin-wife Lysandra with their children fled to Seleucus I Nicator in Babylon.
[22] Ptolemy Keraunos lived in his father's kingdom as a political exile and, prior to marrying Lysimachus' mother, had murdered Seleucus I in order to gain the power of his former protector and then rushed to Lysimachia where he had himself acclaimed king by the Macedonian army.
[23] The union between Arsinoe II and Ptolemy Keraunos was purely political as they both claimed the Macedonian and Thracian thrones.
Ptolemy Keraunos quickly retaliated by capturing Cassandreia and killing Lysimachus and his brother Philip.