As a NRI, Can I add my name in my mothers fixed deposit as a secondary account holder?

I m a Canadian citizen. I have one brother and two sisters. my father passed away. My mother have some funds in fixed deposit in bank. she want to keep full control on her money during her life. She doesn't want to give anything to my brother because he doesn't have Good relationships she don't want to make any will because it can challenge in court easily but she want that her children can get their share easily 1) I m a NRI. can I add my name in my mothers fixed deposit as a secondary account holder under either or survivor in her domestic Indian account? 2) If i can add my name, will i be the only owner of funds of that fixed deposit after her death because account will be under either or survivor? 3)under above situation can any other legal heirs challenge their share in court in that fixed deposit, if can challenge what will be my winning chances as account will be under either or survivor basis? Please guide the best legal way. Thks