Continuity of living right

My Grandfather executed a gift deed of his house to my father on 1986. In that gift deed, he had also granted living rights for life time to my grand mother. My father expired on 1994 with out executing a will. My Grand Mother, my mother , my brother and myself inherited the house as legal heirs. As my brother was in a distant destination with his profession and insisted on settling his part, I settled his part financially. My mother and brother did a release deed of the house to my name. At that time of registration, the document writer insisted that my mother and brother alone has the right to release their shares since the grand mother was granted only living rights by my grand father. So the documentation happened in such a way that my mother and brother doing the release deed to my name. My grand mother was included as a witness. I have fetched all the supporting documents since then. My grand mother expired in 2004. Now I have decided to sell my house, the legal advisor of the buyer is questioning the absence of my grand mothers part in releasing the share since she happens to be legal heir of my father. Seeking your valuable advice on this issue. Was the Document Writer right ?