My sisters asking a part in property

My father died in 1993 without any will. The current home is his self aquired property. But the property is under 99 years lease & yet not owned by us. After the death of our Father & Mother, our two sister are asking for equal part in property. What can be done in this case. The 7/12 is yet carrying fathers name & the sister is rushing to collector office to add their names. Please suggest.