Issue legal notice to sister to hand over documents relating to deceased mother 

if she refuses take legal proceedings against sister 

1) apply for certified copy of death certificate 

2) apply for certified copies of property documents 

  Obtain duplicate documents of your mother such as Death certificate from the jurisdictional Corporation/Municipality, PAN Card from the jurisdictional Income Tax Department, Aadhar Card from the concerned department and certified copy of Property Card from the jurisdictional District/Sub-Registrar's Office 0r any statutory authority, by producing Genealogical/Family Tree, which undoubtedly proves that you are the children of the deceased person.

1. Death certificate can be obtained from PMC furnishing date and name.
2. You should have some proof of possession of documents by. Proof need not be documentary. It can be evidence of any other sister who saw the document in her possession.
3. You can issue lawyer's notice seeking production of documents referring to evidence of other sister. Warn of legal action under criminal and civil law. This will force  her to produce the documents.

Dear  client 

If your sister is denying that she has the documents related to your deceased mother, you have several options:

Mediation: You can try to resolve the issue through mediation with the help of a neutral third party.

Legal action: If the issue cannot be resolved through mediation, you can consider taking legal action. This may include filing a complaint with the local police or taking your sister to court.

Probate proceedings: If your mother had a will, you may be able to obtain the necessary documents through probate proceedings.

It is recommended that you consult with a local attorney or legal expert for specific guidance on your situation, as the laws and procedures may vary depending on your location.

If you are looking for partitioning the property that was on your mother's name, you can mention all these issues in the suit plaint and file a suit for partition and can request the court to direct the opponent to produce all the relevant documents before the court. 

You are advised to file a suit for partition and obtain the copy of the documents through a court order. 

1. You have no evidence to prove that she is holding those documents.

2. Moreover, you might be asked by the Court, why do you insist that she shall have to part with those documents on your demand copies of which you can collect for the authorities by yourself.

3. So, apply for cop[ies or certified copies of those documents.

1. There is  no way you can prove that she is holding those documents.

2. Collect copies or certified copies of those documents from the appropriate authorities by filing applications.

- You can send a legal notice to her for giving all the documents 

- Further , if she is not having or denying for the same , then you can get the certified copy from the office of the registrar after giving property details. 

- Further, being the legal heirs , you can get the death certificate copy from the registrar as well. 

- Further , if you having apprehension that she may use those documents for her personal needs , then you can publish a missing notice in the newspaper and also can lodge a missing compliant before the police. 

Dear Madam,

Those are joint properties of entire family.  As such one of the member of family can't deny access to other family members.  U may lodge complaint with Police under section 406 of IPC.

You can compel her but if she was in custody should provide it. You can file 406 IPC against her