How do I remove my son's account from Family Sharing?

Re: Family Sharing: "How do I remove my 9 year old sons account from family account?"

See Apple Support's online article (link below) for all the details:

You can delete a child's account, or: Move a child to another group using Family Sharing - Apple Support

Eg: says:

"Children under 13 years old must be part of a family group managed by a parent or guardian.

To remove a child from one group, a parent or guardian needs to invite them to join their group.

Or the current family organiser can delete the child's account.