Yes you can get the duplicate death certificate by applying to the concerned municipal corporation. If you cat yourself so you can hire the services of an advocate.

Sir/Ma’am

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It is not clear why you need your aunt's death certificate and for what purpose. More so, when you say that her paternal family is holding it. Only the nearest family members such as the children of the deceased are entitled to obtain the death certificate of your aunt. 

Be assured that the law does not permit anyone to monopolise or withhold a public document like a death certificate. You are fully entitled to obtain a certified copy independently, even without the cooperation of your aunt’s parental family.

1. Your Right to Obtain a Duplicate Death Certificate

A death certificate issued by the Kolkata Municipal Corporation is a public record under the Registration of Births and Deaths Act, 1969.

This means:

• Any interested person (especially a relative or legal heir) can apply for a certified copy (duplicate)
  
• It is not restricted to the person who originally applied or received the SMS/download link
  
• The “phone number linkage” is only for convenience, not a legal barrier

2. Practical Ways to Obtain the Certificate (Even from Abroad)

You have multiple legally valid options:

(a) Online Retrieval

• Visit the official portal of Kolkata Municipal Corporation
  
• Use:

  • Death certificate number
  • Acknowledgement number
  • Date of death

• Most municipal portals allow search and download or re-issue of certificates irrespective of the original applicant

If download is restricted, you can still proceed with a fresh application.

(b) Apply for a Certified Copy
You can apply for a duplicate certificate by:

• Filling an online/offline application
• Paying a nominal prescribed fee
• Providing basic details (name, date of death, place of death, etc.)

(c) Authorise Someone in India
Since you are abroad, the most practical route is:

• Execute a simple authority letter or Power of Attorney in favour of a trusted person in Kolkata
• They can:

  • Visit the municipal office
  • Apply for and collect the certified copy on your behalf

(d) Through an Advocate
You may also engage a local advocate in Kolkata who can:

• File the application
• Follow up with the municipal office
• Ensure prompt issuance

3. Regarding Withholding of Other Items (Cheque Book, Flat Keys, Laptop)

What you have described raises serious legal concerns. If your uncle has also passed away, then:

• His assets and belongings form part of his estate
  
• No individual (including your aunt’s family) has the right to illegally retain or appropriate them
  

Depending on the situation, remedies include:

• Issuing a legal notice for return of property
  
• Initiating civil proceedings for recovery
  
• In appropriate cases, even criminal complaint for wrongful possession/misappropriation
  

4. Important Strategic Advice

• First, secure all essential documents (death certificates of both aunt and uncle)
• Then assess succession (whether there is a Will, legal heirs, etc.)
• Act promptly to prevent misuse of bank instruments or digital data

Conclusion

You do not need to depend on your aunt’s family at all. With the certificate number and acknowledgement details already available to you, obtaining a duplicate death certificate from the Kolkata Municipal Corporation is entirely feasible and legally your right.

1) Visit the Janma Mrityu Tathya Portal and use the "Download Certificate" option under "Citizen Services".

2) You can also check the status or apply for a digital copy via the West Bengal e-District Portal

3) in alternative You or a representative must apply to the Registrar of Births and Deaths at the

(5, S.N. Banerjee Road, Kolkata - 700013).

4) enclose Application letter explaining the need for a duplicate.

• The Certificate Number and Acknowledgement Number 
• Relationship Proof: Documents showing you are a relative (e.g., your birth certificate showing your father's name, and your father's birth certificate showing his relation to your aunt).

You can get a duplicate copy of your aunt’s death certificate even if her family is withholding it. The death certificates are public records, and access cannot be restricted by relatives.

KMC provides online access to death certificates.

Visit the official KMC Birth & Death portal

Use Death Certificate Number or acknowledgement Number or name and date of Death.

Under the Registration of Births and Deaths Act, 1969, death certificates are public documents.

Any person can apply for a certified copy.

Your aunt’s family cannot legally block access.

As far as Bank Cheque Book, Laptop, Apartment Key is concerned, they are part of your uncle’s estate. If they are withholding them, it may amount to criminal breach of trust and illegal possession of estate assets.

You issue a legal notice to them to return them failing to comply you may take appropriate legal action to recover them.

You can obtain a duplicate copy of your aunt’s death certificate even if the original or download access is with her paternal family. A death certificate is a public record and no private party can legally prevent you from accessing it.

Since you already have the certificate number and acknowledgement number, you should first try accessing it through the Kolkata Municipal Corporation portal by using the search or download option with available details such as registration number, name and date. In many cases, this works without requiring OTP.

If online download is not possible, you can apply for a certified copy of the death certificate. Being in the USA, you may execute a Power of Attorney in favour of a trusted person in Kolkata who can visit the municipal office and obtain a certified extract on your behalf.

You may also send a formal request to the Kolkata Municipal Corporation by email with the relevant details such as name of the deceased, registration number and request for a certified copy. Authorities generally issue such copies as it is an official public record.

The aunt’s family has no legal right to withhold access to the death certificate.

As regards the cheque book, keys and laptop of your uncle, those form part of his estate. If they are being wrongfully retained, appropriate legal steps such as issuing a legal notice and, if necessary, initiating proceedings can be taken.

In summary, you do not require cooperation from the other side and can independently obtain a certified copy of the death certificate through official channels.

Dear client

You can absolutely get a duplicate death certificate even if the original is held by another party.

In your case, since the original was issued out of the Kolkata Municipal Corporation, you have a few options for obtaining a duplicate:

First, using the KMC website, you can submit an online application for your duplicate. Since you already have the certificate number and acknowledgement number, you can easily search for your death certificate by proceeding to the KMC portal and downloading it directly if you have all of your identifying information.

Second, you can have a friend or family member in Kolkata who can go to the municipal office to apply for and obtain a certified copy of the death certificate on your behalf. Generally speaking, if you provide someone with basic identifying information about yourself, they will issue you a duplicate death certificate.

Third, you could email a request for a duplicate death certificate along with the required information about yourself (such as the deceased person’s name, date of death, and death certificate number) to KMC. Many municipal agencies respond to this type of request.

When dealing with your deceased loved one’s bank accounts and property, you may have to follow legal procedures later, but your immediate concern needs to be obtaining your duplicate death certificate.

Thus, getting a duplicate death certificate is legally permitted and relatively easy to accomplish.