Division of properties of my Grandfather having twin marriage.

I belongs to HUF. My grandfather married twice only after death of first wife. He had One son with first wife and four with second marriage. Though ancestal property never divided between my father and uncles. Now situation has arises to divide the property at third generation. I have some legal doubts that how the ancestral proreties will be divided among legal heirs if both wives of my grandfather? 1. some elders suggests that your Grandfather's properties will be divided in two equal parts for both wives and then to their legal heirs equally? Is it true. 2. What are the legal rights about division of Grandfather's ancestal properties as per hindu marriage act, in case of twin marriage? 3. Or it will be divided by equal share for all eligible heirs of both wives of my grandfather and Not by dividing in two part for both wives first and then to their legal heirs equally ?