Answer:
In most jurisdictions in the United States a minor child cannot be disinherited. In most states a surviving spouse cannot be disinherited.
Adult children can be disinherited by will. In some states an adult child must be disinherited by specifically mentioning them in the will. The testator must mention that the failure to leave that child a bequest was intentional. Otherwise, the child can claim an intestate share of the estate. In some states it isn't necessary to mention an adult child at all. You must check the laws in your jurisdiction.