1. Your father can dispose off the property in any manner he likes, including giving it only to you.
2. Best thing for your father would be to gift the property to you by executing a Gift Deed in your favour during his lifetime.
3. Stamp Duty is meagre in case of execution of gift deed amongst the blood relatives.
4. While executing the Gift Deed, in the narration, your father can make it a point to mention, that the reason for gifting the property to you only and the amount of money equivalent to the share you are giving to your brother and the reason for not giving any share in the property to your sister, if any.
5. There will not be any legal problem in future, if the gift deed is property stamped and registered in the Sub-Registrar's Office.
6. There cannot be any legal problem in future from your Aunt & her children reason being your grand father had transferred the title of the property in your father's name by following the legal procedure of registering the property, while he was alive and was of sound mind. Moreover, as per your version, there is a 'WILL' executed by your grand father in which your grand father had mentioned and confirmed that the house belongs to your father only and also clearly mentioned that no right exists for his daughter, as he had performed her marriage by spending sufficient money.