She was the second daughter and third child born to the noblewoman Berenice I and her first husband obscure nobleman Philip.
[12] Archagathus’ maternal grandmother Berenice I, was the great-niece of the powerful Regent Antipater[13] and she was a distant collateral relative to the Argead dynasty.
After his death, Berenice I travelled with her children to live in Egypt, where she eventually married Ptolemy I Soter the first Greek Pharaoh and founder of the Ptolemaic dynasty.
[20][21] Archagathus, his sister with their mother, spent their remaining youth in Egypt, possibly in the court living with Ptolemy I and Berenice I in Alexandria.
[28] We also learn from surviving evidence that Archagathus had a wife, a noblewoman of very high status called Stratonice.
Archagathus and Stratonice on a marble piece, made a dedication of a temenos to Isis and Serapis at Alexandria on behalf of his uncle Ptolemy II and his grandmother Berenice I.