How was Kartikeya born?

How was Kartikeya born? Once, there was a demon named Tarkasura who had recieved a boon from Lord Shiva that his son could only kill him. Bholenath granted him the boon and Tarkasura wreacked havoc in the three worlds. Lord Shiva recently had just got married to Sati Devi. It was getting obvious that Sati and Shiva would have a son but later Sati immolated herself. Tarkasura rejoiced and again started troubling the Devas. Sati then took rebirth as Mata Parvati and married Shiva. Now, Indra along with the other Devas were getting worried about Tarkasura. Indra went to Mount Kailash and told his agony. Then, Lord Shiva with his third eye gave birth to six children. He sent these children to Ganga. However, Parvati said that she would only raise one child. Then, Parvati mixed these 6 children together and a son named Kartikeya was born. He was given a Vel (spear) by his mother. Kartikeya and Tarkasur engaged in a battle where Tarkasur exhausted all his weapons against the son of Parvati. They both fought for a long time until Kartikeya pierced Tarakasur’s heart with his spear, killing him. The gods got really happy and declared Murugan as the general of Devas and god of war. Kartikeya later got married to Valli and Devasena.