International Convention for the Protection of All Persons from Enforced Disappearance, Article 24 

Victims (Families of any person who has been subjected to enforced disappearance) have the right to know the truth regarding the circumstances of the enforced disappearance, the progress and results of the investigation, and the fate of the disappeared person.

Each State Party shall take all appropriate measures to search for, locate and release disappeared persons and, in the event of death, to locate, respect, and return their remains.