How would a web authentication and account management system be built for this requirement? What should be taken into consideration when building such a system?
One way to achieve this is to let more than one person access the account(in the above example both mother and daughter can access the daughter's account, even simultaneously). But this could give rise to lot of security issues. How does one mitigate that? Or are there better ways to implement parental oversight into web accounts?
If your structure allows implementing this cleanly, allowing the parent account to gain a (read-only?) login session to the child account could be an option.
This can be achieved by providing a notification/an indication on how many people are using that account and providing access to the login history?
Isn't that also that case with sharing the account? How is the back-end going to detect that the minor's account is not shared with exploiter(s)?