[T]here once lived an orphaned poor boy called Niu Lang [who lived] with his brother and sister-in-law. The handsome boy owned an old ox that he worked on the field everyday. The ox is said to be an immortal from Paradise who was punished for mistakes in heaven and sent on earth as an ox. The ox liked the cowherd and one day he said to Niu Lang, "You are a nice person. If you want to get married, go to the river and your wish will come true."
When the Cowherd went to the stream, he saw all the seven beautiful daughters of the Emperor who had come down from Heaven to take a bath. Niu Lang was captivated with the beauty of the youngest daughter Zhi Nu and secretly took away her fairy clothes. Without her fairy clothes the youngest daughter could not fly back to the heaven along with her sisters. The cowherd told the fairy that he would return her clothes if she promised to marry him. The girl coyly agreed to marry the cowherd. They lived a happily married for several years and had two children.
One day, the ox felt that his last day was near. He told the cowherd that he should keep his hide for [any] urgent situation after he dies. Meanwhile, the Emperor began to miss his seventh daughter. He sent Zhi Nu's grandmother to bring her back from the earth. The grandmother succeeded in bringing Zhi Nu back to heaven. While the 7th Princess was being taken away to the heaven, the cowboy wore the ox hide and carried his two children in the two bamboo baskets with his wife's old fairy clothes and chased his wife in the sky. To keep the lovers separated forever, the grandmother created a Milky Way between them. The seventh princess was moved to the star Vega in the Lyra (Harp) constellation, while the cowherd with his two children stayed in the star Altair (Flying one) in the Aquila (Eagle) constellation. The star Vega is therefore popularly known by the name of the Weaving Maid Star whereas the star Altair as the Cowherd Star in China. The mother took pity and the two were allowed to meet only once a year on the 7th day of 7th lunar month. It is believed that on this specific day magpies form a bridge with their wings for Zhi Nu to cross to meet her husband. [Source: StValentinesDay.org]