Stock as gift

As  per  Schedule I  (2)  of the CGST  act  2017 ,  supply of goods or services  to  related  party  or  distinct  person made in course of furtherance Business   even without  consideration  will be treated as supply and  GST  applicable . 

confirm with others also.  

Here the point is at what value you do you consider  the stock in your books.But any way, will add G.P while making sale and pay tax on it , hence  you can treat as your expense.

You write off the balance of your brother to capital.