Generally, if a Last Will and Testament cannot be found after the death of a family member (or even a copy of the original Will document), it may be presumed that the person died intestate, i.e. without a Will.
In such a circumstance, the property of the deceased would pass according to the state’s laws of intestate succession, as designated by the Probate Court.
In most states, the typical succession is asset distribution to spouse first, then to children of the deceased. But there are many variations especially when other immediate family members have passed already.
You can search this succession information online for your state, or contact the Probate Court in your county for details.