Her father requested that Cleopatra and his oldest son, Ptolemy XIII, become joint rulers, and made Rome the guardian of the Egyptian state (brother-sister marriages were common among members of the Egyptian ruling house).
Cleopatra was one of six children born to Ptolemy the Flute Player, four girls and two boys. Both boys Ptolemy XIII and Ptolemy XIV didn't live past adolescence. They served as co-throne keepers with Cleopatra VII, as women were prohibited to rule by themselves.
Cleopatra and her brother started a civil war between themselves, which resulted in her being forced into exile to Syria. Her sister Arsinoe accompanied her. In Syria, she raised an army and started back to Egypt to reclaim her throne. In 48 BC she was on the eastern frontier of Egypt with her newly acquired army preparing to attack her brother's army. This battle was never fought because Julius Caesar, who had arrived at Alexandria in pursuit of Pompey, and claimed his right to arbitrate Cleopatra and Ptolemy's dispute as the representative of Rome. When Pompey, fleeing the victorious Julius Caesar, arrived in Alexandria seeking sanctuary, Ptolemy had him murdered in order to ingratiate himself with Caesar. Caesar was so repelled by this treachery that he seized the Egyptian capital and imposed himself as arbiter between the rival claims of Ptolemy and Cleopatra. After a short war, Ptolemy XIII was killed and Caesar restored Cleopatra to her throne, with Ptolemy XIV as new co-ruler (Holbl 120-121).
Cleopatra realized that in order to gain power she would have to remain on good terms with Rome and its leaders, so she successfully set out to seduce Caesar. Caesar wintered in Egypt in 48 BC-47 BC, and Cleopatra shored up her political advantage by becoming his lover. Egypt remained independent, but three Roman legions were left to protect it. Cleopatra's winter liaison with Caesar produced a son whom they named Ptolemy Caesar (nicknamed Caesarion, little Caesar). However, Caesar refused to make the boy his heir, naming his grand-nephew Octavian instead.
Caesar and Cleopatra used each other to gain something, because he wanted to obtain money, and her main concern was gaining power. What had begun as a war between Cleopatra and Ptolemy XIII evolved into a war between Ptolemy XIII allied with Arsinoe, his sister, against Caesar, and became known as the Alexandrian War. Caesar read Aulete's (the flute player) will to Ptolemy and forced him to restore her to the throne. When Ptolemy XIII drowned in the Nile (mysterious, but no reference to her killing or having him killed), Caesar declared that Cleopatra should marry her other brother Ptolemy, then eleven years old, and rule as queen (Chauvaeau) in order to please the Alexanderians and the Egyptian priests. Cleopatra and Caesarion visited Rome between 46 BC and 44 BC and were present when Caesar was assassinated. Before or just after she returned to Egypt, Ptolemy XIV died mysteriously. It's believed that she poisoned him just before he would have reached the legal age at which he could be expected to participate in the government. His death was too opportune to be accidental, because after Caesar's death, her greatest political tie, she still had a tie to Rome,