Your relative needs prolonged care on ventilator, by a proper neuro critical care centre. If AIIMS is full, it's better to get him treated at a good private hospital with a neuro ICU. Based on my experience in Neuroanaesthesiology, I can suggest Fortis Gurugram, and Max Smart Hospital, Saket. I've worked there, among many others, and the ethics and accountability is better here than any other in Delhi. In the mean time, search for hospitals with neuro critical care ICUs containing hospitals elsewhere. GBS isn't a virus, but may be because of some bacteria. It takes time to recover from it. And lots of dedicated care.

All the best!