My grandparents passed away before 2004 without a will. My father is their only son and I have 3 brothers and 2 sisters. How will their property be divided? Will my sisters inherit a share?

Under the Hindu Succession Act of 1956 (applicable before 2004), your father would inherit the entire property as the sole son. Your sisters would not be entitled to any share as daughters were not considered legal heirs in intestate succession prior to 2004.