What is the ruling on five people from the defendant's family swearing an oath that their brother is truthful, with the oath being taken at the shrine of a righteous person, in order to repel harm from an oppressive tribe?

There is no blame on the son in his oath if he is innocent, and there is no blame on the parents if they swear to his truthfulness, whether to attest to his character or based on evidence that indicates his innocence. As for swearing an oath at the grave of a righteous person as a way of emphasizing the oath, this is not permissible, due to the innovation and contravention of Islamic law it entails.