Families as a form of government are legitimately sovereign as they have received their sovereignty from God.
The parents therefore by having sovereignty can enforce authority over the rest of the family by means of set rules or “laws” based on their beliefs and moral values. The parents also have the sanction or permission to discipline their children, exclude any unwanted harmful influence or person, raise money to support their family, emotionally support the whole family, and much more. When the parents raise their children appropriately they will then have heirs who are worthy to take on the family name and inheritance.
I believe God has given families the right to be sovereign over their individual family so that one person or government, possibly the state, won’t have control over a generous percentage of our families. That way just as we individuals are different from one another there will be no family that is exactly the same.