Vishnupurana 4.14.p5

4.14.p5

Sura had a friend named Kuntibhoja who had no son. And to him he presented duly his daughter Pritha. She was married to Pandu and bore him Yudhishthira, Bhima and Arjuna who were in reality the sons of the deities Dharma, Vayu and Indra. And whilst she was a maiden she had a son named Karna begotten by the divine sun. Pandu had another wife named Madri who had by the twin sons of Aditya, Nasatya and Basra, two sons, Nakula and Sahadeva.