It's a great question a but obviously the catch is in "nobody else around" - morality only really comes into play when humans interact with one another. In per

It's a great question a but obviously the catch is in "nobody else around" - morality only really comes into play when humans interact with one another. In perhaps the simplest possible example, they live on land that belongs to a country that defends and otherwise manages it. In that case, paying a basic land tax should be enough. If there are other interactions between the family unit and its society, then other arrangements might need to come into play to allow them to maintain the entitlement for that lifestyle.