Transmission refers to the transfer of securities from the demat account of a deceased holder to that of the surviving joint holder(s), nominee or legal heir. On the death of a joint holder of a demat account, the surviving holder or holders become entitled to the securities.

2) Even as per the applicable provisions of the National Securities Depository Ltd (NSDL) bye-laws, in the event of the death of a joint holder of a demat account, NSDL will recognize the surviving holder(s) as having title to the security balances lying to the credit of that account

3) as legal heir of father apply for succession certificate in respect of shares held by father jointly with your uncle 

You can apply for Succession certificate in the court and apply for that Demat account to be inactive or dormant stage as of now. 

When one of the joint account holders passes away, the surviving holders shall succeed in the securities and funds standing to the credit of such an account.

• Lock-in shares will only be moved to the surviving holder(s) CDSL demat accounts.
• The surviving holder(s) can transmit securities to an account opened in their names only.

The articles usually state that only the surviving shareholder on the register of members will be recognised as having title to the shares.

The Company shall on receipt of the death certificate along with a request letter and all share certificates, shall delete the name of the deceased shareholder and return the share certificate(s) duly endorsed in favour of the remaining shareholder(s)..

You may not have a valid claim in the given circumstances.

You should apply for death certificate of your father 

apply for succession certificate at earliest 

if uncle sells your father share them you can take legal proceedings against uncle 

1. 
   Nature of Joint Demat Account: In the case of a joint demat account, the holdings are typically operated based on the principle of "either or survivor." This means that if one account holder passes away, the surviving account holder can operate the account and may have rights over the shares in the account.
2. 
   Transmission of Shares: However, the shares held in the name of your deceased father do not automatically become the property of the surviving joint holder (your uncle). Instead, they should be transmitted to the legal heirs or the nominee of the deceased holder. If your father had nominated someone, the shares would be transferred to the nominee. In the absence of a nominee, the legal heirs would need to produce necessary documents like a succession certificate or probate to claim the shares.
3. 
   Legal Action: If your uncle tries to sell the shares of your father without proper authorization or without transmitting them to the legal heirs or nominee, it may amount to a wrongful act. You can:

   • Approach the depository participant (broker) and notify them about your father's demise, providing them with a copy of the death certificate. This would place them on notice, and they may take precautions before allowing any transactions on those shares.
   • If your uncle does proceed with unauthorized sales or transfers, you can approach the court for relief. You can file a civil case for injunction (to stop him from selling further shares) and for recovery (to recover the proceeds from any sales he has already made).
   • Additionally, if he acts fraudulently, criminal charges might be applicable, depending on the specifics of his actions.

4. 
   Preventive Measures: To protect your interests proactively:

   • Approach a lawyer to send a legal notice to your uncle, making it clear that the shares of your father should not be sold and must be transmitted to the legal heirs or nominee.
   • Consider obtaining a succession certificate or probate, which will solidify the legal heir's claim over the assets of the deceased.
   • Notify the relevant authorities, including the depository participant (DP), about the death of your father and ask them to freeze any transactions related to his shares until the transmission process is complete.

First of all Please check the nomination form assigned by your father in this demat account.

Once nomination is found in whosoever's name you would be in a better position to claim the stake of your father into the transactions that your uncle and your father jointly held. 

If there is no nomination then address communication to the stock broker, the concerned stock exchange and the companies of which your father and uncle hold the stocks and write them that your father has expired and therefore the stake of your father jointly held with your uncle needs to be transferred in favor of the legal heirs of your father until such transfer is not processed and successfully names are not disclosed in place of your father, supply standing instructions to the stock broker, the concerned stock exchange and the companies not to process any transaction acceded by your uncle as valid without your express consent. 

- As per law, after the demise of your father intestate , his property and assets would be devolved upon all his legal heirs equally and his brother i.e. uncle having no right over his said shares 

- Hence, being the legal heir you can claim his shares , and if uncle creating trouble then you can send him a legal notice to him for transferring the deceased share in your name. 

- Joint holder cannot retains others shares in the account without his or his legal heirs consent. 

- Further, if he refused , then file a case before the court. 

Apply for Succession Certificate. 

You can take order from the court that he can’t sell or transfer the shares by taking injunction order