Right of a Son on Ancestral Property now in the name of Father

A person has three sons, he is living with eldest son the younger son lives separate from home and youngest lives on the first floor of the property of his father constructed by him with no proof of construction as well as no proof of registration available with him. The agreement to sale has already been implemented and after the sale deed implementation the youngest son demands an additional amount over and above the equal share in the property not only that he demands a handsome amount which is not deserved by that place. The father is ready to give amount over and above equal share but the youngest son is not ready to accept the same and demands three times more than offered by the father, and says that he has all the right to demand the same and even he will not vacate the same until and unless his demands gets fulfilled. Whether he can go against the decision of his father if the property belonged to his father's father and his father acquired the property through inheritance? Whether he is correct not to vacate the place in the said case?