Sale/transfer of shares from joint demat account with 1st holder OCI

We 3 siblings (2 brothers, 1 sister) are 3 joint account holders of a demat account with the 1st holder a US citizen with OCI and the remaining 2 account holders resident Indians. The demat account is linked to a joint bank account in the same 3 names, with the same first holder (US citizen with OCI). The demat account contains shares transferred after the deaths of our parents (through transmission, after obtaining necessary court documents) as we are the only 3 legal heirs. Each of us 3 owns 1/3rd of the shares in the joint demat account. As soon as possible, we wish to sell 1/3rd of the shares, transfer the proceeds to a US bank account of the first holder and transfer the remaining 2/3rd of the shares (1/3rd each) to the individual demat accounts of the remaining 2 holders in India. What is the most tax efficient way, assuming the total value of shares is 10 lakhs, between 10 and 20 lakhs or above 20 lakhs?

@Kaushal_Soni @Divya_Singhvi @Laxmi_Navlani @AkashJhaveri can you?