There are no credible sources to show that the North Korean leader Kim Jong Un is in grave danger.
Meanwhile, South Korea’s presidential Blue House said that there are no unusual signs or movements that they witnessed in North Korea and an official of the Chinese Communist Party’s International Liaison Department speaking to Reuters expressed the belief that Kim was not critically ill.
U.S. President Trump said they were not sure the reports are true and his National Security Adviser Robert O'Brien said they are monitoring these reports very closely. Also, the North Korean government sources and media have not officially made any statement in this regard. Hence we cannot confirm if its leader is in critical condition as of now.