How to remove member from family group (usual way not working)?

Hi,

I have 2 logins - a personal one and a family account.

We set up a family group with our family account to set up Minecraft access.

Somehow I have managed to move one child from our family account across to a new “family group” under my personal account/email.

I cannot undo this. I have tried going to my personal family group, clicking … on my child’s profile and “remove from family group” but it says I’m not authorised as I did not add them to the group. I am the only other member of that family and the designated “organiser”.

How can I remove my child from my personal account family group so that I can get them back in the true family group?

Thanks!

:)