Maviarab is correct that no law dictates you have to have your spouse, kids or next of kin in your will. If you want, you can literally leave nothing to your family and give it to someone else.I think you are, but not in games. Kids would be entitled to a part of the loot.
However, I'd like to point out that if you do not have a will, most US states have laws on the books where your belongings will be divvied up between your spouse and kids, or if you don't have them, your closest next of kin. Each state has their own formula on how they divide everything between them.
That's why, please, write a will, get a few witnesses and have it notarized.