Vidura was half-brother to Dhritarashtra and Pandu. He was a son of a maid-servant who served the queens of Hastinapura, Ambika and Ambalika. In some accounts, he was an incarnation of Yama or Dharma Raja, who was cursed by the sage, Mandavya, for imposing punishment on him that exceed the sin.
Both queens were married to King Vichitravirya of Hastinapur, who died childless. Vichitravirya's mother Satyavati was anxious to ensure that the royal line was carried on. She called upon her other son Vyasa, to go to the beds of the two queens to father children. Vyasa was a hermit, and came to the palace, unkempt as he was. He went to Ambika who closed her eyes when she saw him, and to Ambalika who became pale. Hence the children they bore were blind and weak.
When Satyavati asked Vyasa to go to Ambika's bed again, to ensure that there would be children, she placed her maid-servant instead in her bed. The maid-servant was not frightened. Hence her son was not born flawed like his half-brothers. Thus, Vidura was born who was raised as brother of Dhritarashtra and Pandu.
With his half-brothers he was raised and educated by Bhishma, whom they called father.
As he had no royal blood, he was never considered for, or had any chance of obtaining the throne of the kingdom. He served his brothers as a minister.
After Krishna, he was the most trusted advisor to the Pandavas and had warned them repeatedly about Duryodhana's plots. In particular, he warned the Pandavas from Duryodhana's plan to burn them alive in a house of wax he had made for them. He was known for speaking the truth and for his intelligence.
Vidura is famous also for being a true devotee of Lord Krishna. When the latter visited Hastinapura as a peace missary of the Pandavas, he shunned Duryodhana's offer to stay in his stately guesthouse, instead choosing the humble dwellings of Vidura.
In protest against the Mahabharata war, Vidura resigned from the post of minister.
After the great battle, he helped Yudhishtira when he became ruler. Later, he accompanied Dhritarashtra, and his sisters-in-law Gandhari, and Kunti, when they left on their last journey to the forest. He died before his companions, on the banks of the Ganga.