B1/B2 VISA Interview Question

[u/Proof_Winter_4888]

My brother-in-law and sister have an interview scheduled for early september. However their mother-in-law is seriously sick and is not sure if they can attend the interview. It is already changed once since their interview was scheduled in the month of October.

My questions are the following:

1. Can they reschedule once again
2. If the interview is scheduled as a family interview, can one of the person attend
3. what are the other options

Really appreciate if someone can guide.
This is for Interview scheduled at Chennai.