Your brother can indeed gift his portion of stocks to you in DEMAT form. It is legally called "Transfer of Shares".
The Donor (Your brother) has to make an off-market transaction by submitting a DIS (Delivery Instruction Slip) to your joint DEMAT Account provider. (Depository Participant).
The DIS should have the following details:
- Donee's Name.
- Donee’s Demat Account Details.
- Share/Stock to be transferred.
- ISIN Number of the Company.
- Quantity of the Shares to be transferred.
The Donee (you) are supposed to then issue a receipt instruction to your Demat Account Provider (Depository Participant).
Since the account was joint in nature, I believe he can transfer his shares in your name without much of a hassle, withdrawing his ownership in an accompanying application with a Gift Deed on a non-judicial stamp paper, which has to be executed by him, in your favour, mentioning the transactional details of the abovementioned slip.