If you wish to delete your child's Yahoo! account, this article provides the instructions on how to do so. Additionally, if you wish to close your own account, you will need these instructions to close your child account(s) first.  

If your child's account is part of a Yahoo! Family account, you can delete their account as long as you know their password. 

Please note that Yahoo! members have the ability to remove their own account(s) and Account Information from Yahoo!. For the fastest possible resolution to your request, please follow the instructions included below to initiate the deletion of your account.

Before you proceed, please make sure that you want to delete your entire account. In any case, you are always welcome to sign up again for a new account.

By deleting your account, you will lose access to all personalized areas of Yahoo!. This includes Yahoo! Mail, Yahoo! Messenger, Yahoo! Games, Yahoo! Contacts, Portfolio, and any other areas of Yahoo! that can only be accessed with your Yahoo! ID and password. 
 
To get started, please click here and sign in to the account you wish to remove and follow the steps to remove your account. Please be sure to read each page carefully as important information about your account and account information is included. 

If you're having trouble signing in, visit the Yahoo! Password Helper to reset your password.
 
Please complete this process only if you are certain you would like to remove your entire Yahoo! account and any features you have personalized within that account. Once the deletion process is initiated, your Yahoo! account may not be recovered.