In the Hindu epic the Mahabharata, Vidura is the wise half brother of Dhritarashtra and Pandu. The sage Vyasa was his father, and his mother was one of the maids of the queens Ambika and Ambalika.
Vidura never tried to become king, but became a trusted adviser of Dhritarashtra. When Dhritarashtra's sons tried to assassinate the Pandus by having their house burn down, Vidura warned the Pandus and saved them from a terrible fate.
He is supposed to be an incarnation of Dharma-- in other words he is known for his devotion to his rightful duty.