Confusion about who has right to sell deceased parents property

Parents died without a will many years ago, having had 6 children, leaving a property that has yet to be legally transferred or sold. Three of their six children have since also died, their having had children of their own (grandsons). Question - Can the remaining three living children sell the property in order to divide the net proceeds with all, including the family of deceased siblings, or does the family of the deceased siblings (grandsons) also have to agree? One family (the grandsons) does not agree to selling.