Daughter, Makaziwe Mandela, told a court on Wednesday her father's condition is “perilous”, and that he is breathing with the help of a life support machine.
"The anticipation of his impending death is based on real and substantial grounds," the City Press newspaper quoted the court papers as saying.
The government has neither confirmed nor denied whether Mandela is or was on life-support.
Makaziwe was giving evidence during a case involving Mandela's grandson Mandla Mandela, who removed some family members' remains from their graves without permission.
Mandela, who remains critically ill in what is now his fourth week in hospital, had expressed his wish to be buried in Qunu, and his daughters want to have the children's remains transferred so they can be together.
Mandela was South Africa's first black president and stepped down in 1999 after serving one five-year term. He is globally hailed for promoting peace with his former oppressors and fostering racial reconciliation.