If under 13 years old.
Family Sharing - Transfer a child to a different family group - Apple Support
Some people have been able to delete extra accounts using the steps in the articles below. Make sure that you sign out of all your devices to avoid issues with apps that use your Apple ID account or iCloud. After your account is deleted, you can't sign out of iCloud or turn off Find My iPhone Activation Lock on your devices. If you forget to sign out, you might not be able to use your device when your account is deleted.
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
If necessary, contact Apple ID Support for assistance. See the Apple Support articles below for contact information.
Apple ID - Official Apple Support.
Contact Apple for help with Apple ID account security - Apple Support. (Link doesn’t always load)
Get Support Work through the screens to get a chat option. You may have to pick a slightly different problem.
Apple Support schedule phone call
If necessary, try Twitter
https://twitter.com/AppleSupport.
From the Apple Support article below.
Without proof of your identity via security questions and other carefully selected criteria, Apple Support can't help you reset a password or perform any other actions on your account. These policies are audited and reviewed on a regular basis.
Security and your Apple ID - Apple Support.
