Stephen Hawking revealed that the doctors had offered his wife the option of turning off his life support when he was battling pneumonia.

His condition worsened to such an extent that he was put into a drug-induced coma and the Swiss doctors asked permission from his first wife, Jane Wilde, to switch off the life support.
“The doctors thought I was so far gone that they offered Jane to turn off the machine. Jane refused to turn it off. She insisted I be flown back to Cambridge. The weeks of intensive care which followed were the darkest of my life. But slowly the drugs worked, though a small incision in my throat robbed me of my ability to talk. I was then put on a ventilator and hopes of finishing my book seemed over”, Hawking said.
Source-Medindia