1st Story
"Agni, tortured in heat, hands it over to Ganga who in turn deposits it in a lake in a forest of reeds (sharavanam).Then Goddess Parvati,took the form of this water body as she alone is capable of taming the Tejas of Shiva,her consort. . The child is finally born in this forest (vana) with six faces-eesanam, sathpurusham, vamadevam, agoram, sathyojatham and adhomugam. He is first spotted and cared for by six women representing the Pleiades - Kritika in Sanskrit. He thus gets named Karthikeya."
2nd Story
"Agni got unbearable inflammation on his body. He beseeched Lord Shiva for a way to end his agony. Lord Shiva said, "You will be relieved of this affliction when you transfer my vital fluid to the womb of a woman."
Agni retired to a desolate place, waiting for a suitable woman to arrive. He beheld the six Kritikas, all shivering with cold who arrived there. He then transferred Shiva's vital fluid to their wombs. They became pregnant. When their husbands came to know of this, they cursed the six women, to be turned into stars in a constellation in the sky. Before the transformation, the Kritikas aborted their fetuses on the Himalaya mountains. The holy river Ganga carried the fetuses to a secluded place, called the Sara Vana, which was covered with reeds. After some time, Lord Kartikeya (also called Skanda) manifested from those reeds. Since he was born to six mothers, he had six heads. Since he was born in the Sara Vana, he is also known as Saravana.
[Note: The Six Kritikas are the stars of the constellation pleiades. In other texts, Agni carries the six sparks that fell from the third eye of Shiva, not his vital fluid. The sparks are deposited in a pond in the Sara Vana, where a six babies are born on a lotus each. The Krittikas who came there, nursed the babies. When Parvati and Shiva came there, Parvati took all the babies in her arms and made them into one, albeit with six heads."