Grand-daughter of Berenice I
Daughter of Magas I of Cyrene
Wife of  Ptolemy III
Mother of Ptolemy IV & Arsinoë III

When her father died (250 BCE) Berenice's mother arranged her marriage to Demetrius "the Fair," handsome youngest son of Antigonid ruler of Macedonia, Demetrius Poliorcetes. But after her husband was installed as King of Cyrene, he became her mother's lover, so Berenice had him assassinated (249 BCE). Her father's half-brother, Ptolemy II, then arranged her marriage to his son & heir, Ptolemy III, to reunite their two kingdoms. Ironically, soon after her 2nd husband died of natural causes (222 BCE), her oldest son had her killed, along with his siblings.  

Reference: Justin, Epitome of the 'Philippic History' of Pompeius Trogus 26.3.

Other online resources:

• Berenice II of Egypt - well-researched biographical entry in Wikipedia's web.

• Berenice II - Christopher Bennett's annotated Egyptian Royal Genealogy provides detailed references & sources.

• Berenice II - Jona Lendering outlines basic biographical data & chronicles events [Livius: Articles on Ancient History].