Regarding provisions of gift if you all receive any amount in gift from a non relative and it's stamp duty value is above 50000 then you have to pay tax on such gift so first you will have to calculate whether his share which should be around 8.3333% in the land. Does this value comes above RS. 50000 if yes then there is a question of paying tax on such gift. You must also consult with an advocate whether such unregistered will of your sister where it is mentioned that the junior will get 50% share is it a valid will. In case it's a valid will there is no other option but to get his rights relinquished and pay the capital gain tax.