Transfer ownership after mother's death.

The house in which I stay was on my mothers name, I have been staying here with my family since 1996. The initial payment was done by my brother, but due to financial difficulties he transferred the ownership to my mother, via a signed letter given to the builder. Since she could not pay further installments I gave her the cash and bought this house from her, but unfortunately I did not bother to do the paperwork and have no receipt to show payment. My mother died in 1998. We have diligently paid all taxes, maintenance and other household bills for last 20 years. The share transfer certificate shows the house being transferred to my name, but it doesn't have my mothers signature (Is this ok?), because it was prepared after her death. It has the stamp of the housing coop society with signatures of the then Chairman and Secretary. Now my relations with the brother have soured. And I want to make sure all the legal documents are in place that show I am the owner. My two sisters are willing to sign an affidavit or any other relevant document that you may suggest to show legally that the property is mine and they have no objection to it. But I cannot get the same guarantee from my brother. Please suggest what are my options to get the paperwork done without involving my brother?, since I apprehend he may misuse the current situation to disadvantage me. Thanks in advance. Awaiting your reply.