All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
What your father did is unacceptable because it is fear of the future, which none knows but Almighty Allah and opening the door for future possibilities will undermine justice.
Therefore, the sons should give their sisters what is equivalent to their shares in the inheritance, as if the wealth is still in the name of their father. They can also win their sisters` hearts with a fair compensation and not just talk. And Allah The Almighty Knows Best.