He was a son of Ptolemy VIII and Cleopatra III, and younger brother of Ptolemy IX. His birth name was probably Alexander.

Ptolemy X was the second son of Ptolemy VIII and Cleopatra III. When Ptolemy VIII died in 116 BC, Ptolemy IX became king with Cleopatra III as his co-regent and Alexander was sent to Cyprus to serve as governor. However, in 114-113 BC, he declared himself king. Cleopatra III quarrelled with Ptolemy IX and arranged for Alexander to return to Egypt