Is the guest house in ISI Kolkata given to parents of ISI students? For how many days?

Yes, students at ISI are eligible to apply for a guest house accommodation for their parent(s). This completely depends upon the tenure of the stay and the availability of the rooms at the guest house. Basically, there are all these conferences taking place from June to December every year.

• As official requests (conferences, meetings, etc.) are followed by the student requests, it is usually difficult for the latter to be approved during these months. So, getting a guest house might not be an easy task.
• Relying on a guest house would not be appropriate in such a case and it is better to book a hotel.
• Moreover, you can see a lot of highly qualified people including faculty, foreign industry personnel, and exchange students coming and going within the campus. So, the rooms are primarily booked for them.

Therefore, it is suggested you book a hotel. I am sure you might have got a clear idea about the facility assisted for the stay. It would be feasible to prefer other options in case first is not available.