How do I delete a member from my family group

If under 13 years old.

Family Sharing -  Transfer a child to a different family group - Apple Support   *

If 13 or older, see the Remove section.

Family Sharing - Leave.  *

If you want to delete the Apple ID, some people have been able to delete extra accounts using the steps in the articles below.

How to delete your Apple ID account.   *  

Apple ID – How to Delete.  -

Delete Apple ID (new).   -

What to do after you change your Apple ID or password - Apple Support   -