Vyasa Impregnates a Maidservant, Resulting in Vidura

When the eldest daughter-in-law, Ambika, was again in season, Satyavati again asked her to go to Vyasa. But the queen, who was as beautiful as a goddess, remembered the sage's form and odour. Out of fear, she refused. Instead, with her own ornaments, the daughter of the king of Kashi bedecked a maidservant, making her look like a beautiful apsara (celestial dancer), and sent her to Krishna Dvaipayana — Vyasa. When the rishi arrived, the maidservant arose and paid him her respects. Having served him respectfully, she united with him with his permission. His desire satisfied, the rishi was greatly pleased with her. Having spent the night with her, the maharshi arose to leave and told her, "O fortunate one! You will no longer be a servant. The child in your womb will be devoted to dharma (righteousness), and in all the worlds, he will be supreme among those who are intelligent." This son of Krishna Dvaipayana was known by the name of Vidura, the extremely wise brother of Dhritarashtra and Pandu. As a consequence of a curse imposed by the great-souled Mandavya, Dharma (the god of righteousness) himself was born as Vidura. He was learned in all principles, free from anger and desire. Vyasa, freed from the debt he had contracted to his mother, met Satyavati and told her the woman had conceived. Then he vanished. Thus, through Dvaipayana, sons were born in Vichitravirya's field. They were as radiant as children of the gods and extended the Kuru lineage.

Vyasa Impregnates a Maidservant, Resulting in Vidura

Bhishma's Vow and the Kuru Succession Crisis