Kleopatra I Syra
Kleopatra I Syra (Greek: Κλεοπάτρα Σύρα) was a queen consort of King Ptolemaios V Epiphanes of Egypt and the mother of King Ptolemaios VI Philometor of Egypt, Queen Kleopatra II of Egypt, and King Ptolemaios VIII Euergetes II of Egypt. She was a daughter of King Antiochos III Megas of Syria and Laodike III.
Prophecy granted to Daniel
During the reign of King Cyprus of Persia, an angel told Daniel about things to come. The angel told Daniel of a king of the North who would attempt to subjugate the South by marrying his daughter to the king of the South.
Syria is believed to be the kingdom of the North, and Egypt is believed in be the kingdom of the South. Kleopatra is believed to the the "daughter (of women)" mentioned in the prophecy.
He will be determined to come with the power of his entire kingdom, and propose equitable conditions and terms of peace, which he will put into effect [by making an agreement with the king of the South]. He will also give him his daughter (Cleopatra I), in an attempt to overthrow the kingdom, but it will not succeed or be to his advantage.— Daniel 11:17 (AMP)
The angel also told Daniel that a commander would defeat the king of the North.
The king of the North during the foretold time is believed to be Antiochos III, and the commander who defeats the king of the North is believed to be Lucius Cornelius Scipio Asiaticus of Rome.
After this, he (Antiochus III the Great, King of Syria) will turn his attention to the islands and coastlands and capture many [of them]. But a commander (Lucius Scipio Asiaticus of Rome) will put an end to his aggression [toward Rome’s territorial interests]; in fact, he will repay his insolence and turn his audacity back upon him. Then he will turn back toward the fortresses of his own land [of Syria], but he will stumble and fall and not be found.— Daniel 11:18–11:19 (AMP)
Her father's scheme
King Antiochos III Megas of Syria invaded the territory of King Ptolemaios V Epiphanes of Egypt in the Fifth Syrian War. Antiochos defeated the Egyptians in the Battle of Panium. Antiochos III and Ptolemaios V then made peace with each other, and Ptolemaios V married Antiochos III's daughter Kleopatra.
Antiochos III was not able to make any further gains against Egypt, however. After making peace with Ptolemaios V, Antiochos III turned his attention towards Asia Minor and Greece. Antiochos III entered Greece, which was being dominated by the Romans. The Romans defeated Antiochos III at Thermopylae, and Antiochos III was forced to retreat from Greece. Scipio Asiaticus pursued Antiochos III and defeated Antiochos III at Magnesia. In the Treaty of Apamea, Antiochos III had to cede Seleucid territories north and west of the Taurus Mountains to Rome's allies, restrict the composition of his army and navy, turn over fugitives and prisoners, and pay war indemnities. Antiochos also had to turn over his youngest son Antiochos IV Epiphanes to the Romans as a hostage.
Thus, the things foretold to Daniel came to past: Antiochos III married his daughter Kleopatra to Ptolemaios V but did not gain anything from it, and a (Roman) commander defeated Antiochos III, forcing Antiochos back into Syria.
Regency and progeny
When her husband Ptolemaios V died, Kleopatra I's young son Ptolemaios VI become king of Egypt, and Kleopatra became his regent. Ptolemaios VI became known as Philometor ("mother-lover"). After Kleopatra I's death, Ptolemaios VI married his sister Kleopatra II, and after Ptolemaios VI's death, Kleopatra I's other son Ptolemaios VIII Euergetes II became king and married his brother's widow and sister Kleopatra II.