Vidura born

Janmajeya wanted to know why Yama needed to born on earth.
The sage said:
There was a sage called Mandavya. He was meditating below a tree, observing a vow of silence.
Some robbers happened to be in the city and they were fleeing after robbing many houses. The chief of guards was chasing them.
The guards saw the sage meditating and asked him if he had seen the robbers. The sage remained silent.
They saw the loot which the robbers had hidden there. Thinking the sage was the chief of robbers, they caught him.They caught the robbers and along with the sage tied them and presented them in teh court.

The king ordered them to be impaled on spears. The sage was silent all through out.

Some other sages saw this and trying to free Mandavya but were unable to do so. They went to the king and told him that he had wrongfully impaled a sage.

The king ashamed came to the sage and begged his forgiveness. The king tried to take the spear out but was unable to do so.

The sage forgave the king.

The sage then wanted to know why he had to undergo through such a suffering. He approached Yama, who was also the God of Justice, Dharma.

Yama said as a child you used to impale innocent insects on needles, which is why this punishment.

The sage that act did not deserve such a big punishment. As a play of an innocent child, a lighter punishment would have been more apt.

The sage cursed Yama to be born as a human.

This is why Yama was born as a human, as a son of a Shudra woman. Thus was born Vidura.

The blind prince was Dhritarashtra and the pale prince was Pandu.