Maybe just for this Russian citizen needs, in addition to a passport, to have the consent of the parents (or those who by law replaces them) for his departure for border. The document must be notarized, it should contain information about the state in which the child is sent (in this case, China), the travel dates and passport details of the parents / guardians themselves.

If the consent is formalized and given by only one parent, this will be enough if the latter has never previously officially stated that he does not agree that the child would travel outside his country.