In some states dying intestate (without a will) causes your estate to be split 50/50 with 50% going to spouse and the other 50% going to the kids (split evenly). There are different rules in each state.

For instance in Illinois, spouse gets half and kids get half (copied and pasted):

Illinois

If you have a spouse but no children, the spouse inherits everything. If you have children but no spouse, the children inherit everything. If you have a spouse and children, the spouse and the children receive half of your property each. If you have parents but no spouse, children, or siblings, your parents inherit everything. If you have siblings but no spouse, children, or parents, the siblings inherit everything. If you have parents and siblings, but no spouse or children, your property is evenly divided among each parent and each sibling. (However, if you have only one parent alive, that parent receives a double share.)