Initially she was only called Selene and added the Ptolemaic throne name Cleopatra after her marriage with Lathyros. In Egypt, she was married to Lathyros after his wife, her sister Cleopatra IV, was pushed out by her mother (115 B.C.). She was not made co-ruler, unlike the many sister-wives of Ptolemaic kings. She bore Lathyros Berenice III and two sons, perhaps Ptolemy XII and another son, named also Ptolemy. (All the male kings and princes in Ptolemaic dynasty were named Ptolemy, as the founder of the dynasty, Ptolemy I (greek : Πτολεμαίος, which meant "warrior"), who was one the generals of Alexander the Great).
In 107 B.C., as relations between Lathyros and his mother and co-ruler, Cleopatra III, were getting worse, Cleopatra's III intrigues forced Lathyros to leave Egypt and his wife. He went to Cyprus to raise an army, and then to south Syria. From there, he tried, in 103 B.C., to invade Egypt. Cleopatra III set an alliance with one of the two quarreling kings of Syria, Antiochus VIII Grypus, and gave him Cleopatra Selene I as his wife. Grypus' previous wife, Cleopatra Tryphaena, who was Cleopatra Selene's I older sister, had been killed in 111 B.C. by Grypus' step-brother Antiochus IX Cyzicenus.
In Syria, the civil war between Grypus and Cyzicenus over the throne in Antioch lasted until 96 B.C., and exhausted financially the country. In 96 b.C. Grypus was assassinated in Antioch, and, so, Cyzicenus captured the capital and married Cleopatra Selene I. (Cyzicenus had been married with Cleopatra Selene's I older sister, Cleopatra IV, but she was killed by Grypus in 112 B.C.)
However, Cyzicenus was not to live for a long time. Grypus had five sons with Cleopatra Tryphaena and all of them wanted the throne of Antioch. In 95 B.C., Cyzicenus was killed during a battle with Seleucus VI Epiphanes, the older son of Grypus.
After Cyzicenus death, his son with Cleopatra IV, Antiochus X Eusebes, married his stepmother, Cleopatra Selene I, and regained Antioch again, while Seleucus VI was killed. Against what was expected, the marriage was "real" and Cleopatra Selene I bore two sons, and one of them was the later Antiochus XIII Asiaticus.
Antiochus X was killed either in 92 B.C. in a battle with the Parthians, or in 83 B.C. After his death Cleopatra Selene I feared for her safety, left Syria and stayed in Cilicia.
After the assassination of her nephew Ptolemy XI Alexander II (80 B.C.) Cleopatra Selene I was the only surviving legitimate member of the Ptolemaic family. She claimed the throne of Egypt for her sons from her fourth marriage, but the people of Alexandria chose the illegitimate Ptolemy XII Auletes as new king. Cleopatra Selene I sent her sons to Rome to present their claims before the senate, but they had no success and had to return home two years later. Finally, in 69 B.C. the Armenian king Tigranes the Great besieged Cleopatra Selene I in Ptolemais, seized the old Queen after the capture of the city and killed her brutally in Seleucia.
One year later, the Romans disrupted the Armenian state, and Cleopatra Selene I's son, Antiochus XIII, the last king of the Seleucid dynasty, tried unsuccessfully to unify the state. Finally, in 63 B.C., the Romans captured Syria and the Hellenistic state that Seleucus I Nicator (greek :Σέλευκος Νικάτωρ) created 240 years ago, became part of Rome.