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The Sambhava Parva of Mahabharat mentions which gods and demons incarnated on earth at the time of Mahabharat giving details about even obscure kings. Curiously enough it does not mention anything about the previous births of Pandu and Dhritrashtra though it does mention that Vidura was the personification of Dharmaraj:
He who was known as Dhritarashtra born of the seed of Krishna-Dwaipayana, and gifted with long arms and great energy, also a monarch, of the prophetic eye, became blind in consequence of the fault of his mother and the wrath of the Rishi. His younger brother who was possessed of great strength and was really a great being known as Pandu, devoted to truth and virtue, was Purity's self. And, O king, thou shouldst know that he who was known on earth as Vidura, who was the first of all virtuous men, who was the god of Justice himself, was the excellent and greatly fortunate son of the Rishi Atri.
So my question is - Is it mentioned anywhere in the Mahabharat or any other scripture what the previous births of these two sons of Ved Vyas were?