Since no contemporary accounts exist of Cleopatra's life, it is difficult to piece together her biography with much certainty. Much of what is known about her life comes from the work of Greco-Roman scholars, particularly Plutarch. Born in 70 or 69 B.C., Cleopatra was a daughter of Ptolemy XII (Auletes). Her mother was believed to be Cleopatra V Tryphaena, the king's wife (and possibly his half-sister). In 51 B.C., upon the apparently natural death of Auletes, the Egyptian throne passed to 18-year-old Cleopatra and her 10-year-old brother, Ptolemy XIII.
Soon after the siblings' ascension to the throne, Ptolemy's advisers acted against Cleopatra, who was forced to flee Egypt for Syria in 49 B.C. She raised an army of mercenaries and returned the following year to face her brother's forces at Pelusium, on Egypt's eastern border. Meanwhile, after allowing the Roman general Pompey to be murdered, Ptolemy XIII welcomed the arrival of Pompey's rival, Julius Caesar, to Alexandria. In order to help her cause, Cleopatra sought Caesar's support, reportedly smuggling herself into the royal palace to plead her case with him. Caesar and Cleopatra
For his part, Caesar needed to fund his own return to power in Rome, and needed Egypt to repay the debts incurred by Auletes. After four months of war between Caesar's outnumbered forces and those of Ptolemy XIII, Roman reinforcements arrived; Ptolemy was forced to flee Alexandria, and was believed to have drowned in the Nile River. Entering Alexandria as an unpopular conqueror, Caesar restored the throne to the equally unpopular Cleopatra and her younger brother Ptolemy XIV (then 13 years old). Caesar remained in Egypt with Cleopatra for a time, and around 47 B.C. she gave birth to a son, Ptolemy Caesar. He was believed to be Caesar's child, and was known by the Egyptian people as Caesarion, or Little Caesar.