Release deed

Need advice on the following

My mother, my wife and I were co owners of an apartment in Thane. My mother passed away 5 years ago. There is no will. My sister and I are the only two siblings. 

My question is that will a release deed e sufficient for selling the said apaertment. or would it need a succession certificate. Secondly would a release deed also be required for obtaining the succesion certificate

Thank you

Sanjay