Pandu led an austere life in Forest. However, he was melancholic in his heart for being childless. Once he tried to convince Kunti to get impregnated with a saint for the sake of continuing the clan. After several requests, Kunti began to invoke three Gods for the same purpose. Thus she delivered Yudhishthir after invoking God Dharmra, Arjuna by invoking Indra and Bheem by invoking Pawandev. By the same procedure Madri delivered two sons Nakul and Sahdev by pleasing Ashwini Kumar. It means Pandu was not the Father of “Pandvas” : the five brothers. Later Kunti worshipped the Sun and got blessed with a son Karna too. Thus Kunti had four sons while Madri had two sons.
Once during monsoon Pandu and Madri were taking a stroll in a forest. Suddenly lust seized him and he could not resist the temptation. He started sexual intercourse with Madri. As per the curse, It resulted in death of Pandu. Madri was unable to bear the shock of his death and offered herself to the balefire. Thus the responsibilities of raising Pandavas fell squarely on Kunti. Instead of visiting her maternal home, Kunti decided to go Hastinapur. She was welcomed there and Pandvas were accepted as sons of Pandu. This prompted an another set of competition and confrontation, as Gandhari, the wife of Dhritrashtra, had her own ambitions