God Surya’s illegitimate children were many and included Karna, son of Kunti in the Mahabharata and Sugriva, the monkey king who became the helper of Rama in the Ramayana. One of his sons became the ancestor of the solar race. His most famous progeny were the children of his wife Sanjna. The story of Sanjna and Surya repeats with variations the myth of Vivasvat and Saranyu. Sanjna was the daughter of Visvakarma. In early years of their marriage she bore Surya three children. These were the Manu Vaivaswata and the twin Yama and Yami, who became the first man and woman and, later, deities Yama, king of the dead and Yami, identified with Yamuna, goddess of the River Jumna.
But as time passed, Sanjna found the brilliance her husband's presence insupportable and she fled, leaving her handmaiden Chhaya (Shade) in her place. In her retirement Sanjna lived in the forest disguised as a mare and devoted herself to religious exercises. After some time Surya spied her out as she was grazing in a field; he took the form a horse and approached her. From this union were born the twin horsemen, the Aswins, and another, less important son called Revanta. The character of the Aswins differs little from the Vedic conception, though perhaps their role as luminary deities is stressed less than that as physicians of the gods. For some time Surya and Sanjna lived together as horses, but they finally tired of life as animals and changed back into human form. Surya now brought his wife home with him and agreed in order to prevent recurrence of her flight, that his father-in-law Vishvakarma should place him on his lathe and shave away an eighth of his brightness, from every part of his body except his feet. Thereafter the couple lived happily together.