Contentious youngest son of Ptolemy V & Cleopatra I whose feuds with his brother [Ptolemy VI Philometor] & sister [Cleopatra II] divided the Ptolemaic empire & invited Roman intervention.  An unpopular ruler, he was often referred to as Physcon ["pot-bellied"] rather than his official honorific byname, Euergetes ["Beneficent"].

Ptolemy VIII became co-ruler of Egypt at age 12 in 170 BCE, but six years later tried to claim sole rule for himself by expelling his older brother & sister. His victory was short-lived, however. For, within a year, he himself was driven from Alexandria by an Egyptian mob.  In an effort to restore peace, Rome returned Philometer & Cleopatra II to the throne of Egypt but granted Cyrene [Libya] to Physcon (164 BCE). For the next decade Physcon tried to take control of Cyprus, but was decisively defeated by Philometer (154 BCE). The older sibling's death  (145 BCE), however, revived the ambitions of the younger.

Recalled to Egypt, Physcon married his brother's widow & eliminated his young nephew [Ptolemy VII]. This marriage of royal siblings, however, was merely a political move. After years of quarreling with his sister, Physcon was again expelled from Alexandria in 130 BCE along with his niece [Cleopatra III], whom he had elevated to the position of consort, -- this time by a jealous Cleopatra II, who claimed sole rule for herself.  Physcon returned the next year, however, driving his sister-wife into exile in Syria (127 BCE). A truce between the aging rivals was finally negotiated in 124 BCE, restoring Cleopatra II as dowager queen of Egypt. After 40 years of civil war, however, the Ptolemaic dynasty was left with only a shadow of its former power. Physcon's will weakened it further by partitioning Egyptian territory among his widow & his sons.

References: Josephus, Antiquities 12.235, 243; 13.267-268; 14.250.
                   _____, Apion 2.51-54.
                   Justin, Epitome 38.8; 39.2-3.

Other resources on line:

• Ptolemy VIII Euergertes II - chapter 10 of E. R. Bevan's 1927 classic The House of Ptolemy [on Bill Thayer's Lacus Curtius]. 

• Ptolemy VIII - Christopher Bennett's annotated Egyptian Royal Genealogy provides detailed references to sources.

• Ptolemy VIII Physcon - Jona Lendering lists biographical data & key dates [Livius: Articles in Ancient History].

• Ptolemy VIII Physcon - entry in Wikipedia's web.