Hello again,
so I had this issue some time ago, and also got a fix talking to microsoft assistance which finally did not work.
However, I got an email right after my birthday, sent from Microsoft Family service where they notified me (as a parent) that my child (also me) just turned 19, so that he (actually, me) can now control his own settings in parental control which might override the settings I (as a parent) made. So, all in all
- Microsoft thinks I am my own child
- Microsoft thinks that we have the same birthday, and
- Microsoft keeps a record that I am now 19 (so, my birth year is 1999) -> seems like "another y2000" bug to me.
Anyhow, I did not see this annoying pop-up window ever again since that. So, hopefully, until dec.31 this year you all guys will turn 19, and this issue simply will get solved by time. :D