Ptolemy Keraunos
At Ptolemy II's birth, his older half-brother Ptolemy Keraunos was the heir presumptive. As Ptolemy II grew older a struggle for the succession developed between them, which culminated in Ptolemy Keraunos' departure from Egypt around 287 BC. On 28 March 284 BC, Ptolemy I had Ptolemy II declared king, formally elevating him to the status of co-regent. In contemporary documents, Ptolemy is usually referred to as 'King Ptolemy son of Ptolemy' to distinguish him from his father. The co-regency between Ptolemy II and his father continued until the latter's death in April–June 282 BC. One ancient account claims that Ptolemy II murdered his father, but other sources say that he died of old age, which is more likely given that he was in his mid-eighties.