Octavian was always one of the main political contenders in Rome. He was younger than the others but VERY ambisious and self involved, always doing whatever was in his self interest.

After Ceasar was murdered by the senate, Cleopatra-VII was still of the Egyptian Pharaoh of the Ptolemaic Dynasty. Cleopatra returned to Egypt, which had become run down in her absence. Cleopatra tried to bring her contry back to it's previous glory.

At that time Rome was threat to Egypt's sovencry. Cleopatra watched to see who would be the next power in Rome. After Brutus and Cassius had been killed, Antony and Octavian went back to Italy very ill, so Antony was the one she had to watch.

Cleopatra enchanted Marc Anthony (who actually controles a third of Rome, including Egypt)

Meanwhile back in Rome Octavian contrived to have Marc Anthony marry Octavian's sister, Octavia so he would have more control over Marc Anthony. In 40 BC, Mark Antony left Cleopatra and returned to Rome to marry Octavia, and did not see her for four years. In 32 to 31 BC, Antony finally divorced his wife, Octavia the sister of Octavian, and returned to Cleopatra.

Octavian was non too pleased with that and incited the Romans against Cleopatra. Octavian was in the power struggle and accused Cleopatra of witchcraft in controlling Marc Anthony and used this as an excuse to attack Egypt.

Octavian had several battles with Antony. Antony half-heartedly defended Alexandria against the advancing army of Octavian. After the defeat, Antony committed suicide by falling on his own sword in 30 BC.

Octavianus is now in Alexandria, Marc Anthony falls on his sword, he still wants to capture Cleopatra alive. He also fears that she would let her mausoleum burn into flames to avoid her treasury to be stolen. He wants her alive to take her to Rome, to show his superiority and his victory.
Cleopatra stays in her mausoleum, Octavianus sends of his man who manages to enter the mausoleum and capture Cleopatra. The mausoleum is now Cleopatra's prison, it's a safe place to hold her captive until the long way back to Rome.

After Antony's death, Cleopatra was taken to Octavian where her role in Octavian's triumph was to be displayed as a slave in the cities she had ruled over. He had no interest in any relationship, negotiation or reconciliation with the Queen of Egypt.

Cleopatra's children are also captured except Caesarion who fled to the south. She really wants to die but she has no weapon to kill herself. She begins a hunger strike, she rapidly weakens but Octavianus threatens her: if she dies, her children will be killed. She accepts to eat again but she's still weak.

Octavianus is now persuaded that she wants to stay alive. The departure for Rome is in three days, just enough for Cleopatra to prepare her suicide. She asks her servants Iras and Charmion to bring her a snake in a fruit basket.

She would not live this way, so she had an asp, which was an Egyptian cobra, brought to her hidden in a basket of figs. She died on August 12, 30 BC at the age of 39.

With the death of Cleopatra, The age of Egyptian Pharaohs was replaced by Roman Emperors. Octavian was the first.

After their parents died because of Octavian. Caesarion was betrayed by his tutor, Rhodon, on their way out of Egypt. He was then killed on Octavian's orders. After Cleopatra's death, Caesarion was strangled as he was heir to Cesaar's heir and a threat to Octavian's ambisions.

The other children (Seline "The Moon" and Helios "The Sun" were raised by Antony's wife, Octavia. Octavia was the sister of Octavian. Octavia had always been loyal to Marc Antony, apparently even after the divorce.