I had a friend who went through this, well many friends but this one had an interesting story. I hope that it does not come in helpful anytime soon.
His Mother was in a coma and the Doctors said that she was not going to recover. The kids took turns sitting with her. After three days a nurse pulled them aside and told them that they had seen many a case that a Mother has not been willing to pass when her children or grandchildren are in the room. She suggested that they all go out to dinner. While they were eating, their Mother passed.
Apparently it is not unusual for a mother to fight to live when her children are present. She simply cannot bear the thought of leaving her kids.
Hopefully you don't have to deal with this right now but if you do it might be a good time to have a nice dinner with your siblings and reflect on you Mothers life.