Hindu Succession Law

My father died 17 years ago(1999) leaving behind his wife,2 minor sons and a mother and no will.He died in then state of Bihar,but his body was cremated in his native village in Bengal My 70 year old grandmother refused any share of property or any partition orally.She died 2 years later in 2001 leaving behind 4 sons and daughter.During the two years she was alive her entire expenses were borne by us including the expenses for all rituals post her death. My mother was a nominee in all his bank accounts,lockers,FDs and movable properties and has been transferred to my mother. My father also held a property in another state Odisha which he bought from his own earning which we now want to transfer to our name.We have a legal heir certificate from the Gram Panchayat and an affidavit issues by a 1st class magistrate on basis of that certificate which states that the legal heirs are me,my mother and my brother.Both the certificate and the affidavit were issued after my grandmother had passed away.Is there anything else that is needed to get the said property transferred in our names?If yes then what and how do we get it?Also is there anyone else who can claim to be a legal heir?Since my Grandmother is now dead and she never filed for any partition or succession or made any claim to any property that my father had. All of three of us are presently residents of bengal.Our lawyer is of the opinion that since this is immovable property a succession certificate isnt required.