Brother trying to cheat

We are 3 sisters and one brother. Our mother passed away in Jan16, and our father who had a brain stroke a year back also passed away recently in Jan17. Unfortunately, they did not prepare any WILL, but just before his demise our father had expressed his WILL verbally to the eldest daughter about equally distributing his wealth to all his children. This was video-recorded by my sisyter. My brother is the nominee in all their bank savings account, FD, Demat account etc. They also have a 3BHK flat in Kolkata which is occupied by my brother who was living with them. Now, despite several emails, reminders etc. my brother is not ready to share the information about our parents' assets with us. I suspect he has already withdrawn all the FDs, bank balance as he is the nominee and now trying to cheat us. I know that I am entitled to equal share as a Class 1 legal heir, but he is not co-operating. I will probably need to take recourse to legal action against him now. Hence, need some advice on next steps now.