Clarification on legal heirs of a deceased Hindu male

My father is an Hindu male died intestate in 1995. He had self acquired a property. My father had 2 sons and 6 daughters and I am one among the daughters (aged 68 yrs). One of his (father) married son pre deceased him in 1986. Currently, we are only two daughters surviving as class 1 legal heirs and all my other married siblings have died. Please clarify me, who are the rightful heirs to sell the property. Do the children's of my late siblings too are rightful heirs? Are they also required to sell the property? Buyers demand to get sale deed executed by all legal heirs including heirs of died siblings. PL clarify how to proceed with this.