Help with family estate questions?

5 Years ago my grandmother ped away. Over the past 5 years my aunt has attempted to settle the estate by buying the house. and distributing the amount from the sale equally to all heirs of my grandmother's estate. She hasn't included any bank accounts or insurance monies with this and is only dividing the monies from the sale of the house. What is my father and his other siblings entitled to? When seeking legal advice what should he ask for? On the paper work from the lawyer handling the sale it mentions and executor (one who carries the will) but my aunt claims there is no will...who would the executor in the case possibly be?