Accessing the Niantic Kids Parent Portal doesn’t require a password.
To access the parent portal and manage your child’s account, visit this page and enter the email address you entered to give your child permission. This will send you an email containing a login hyperlink that allows you to access your account without inputting a password. 

If you do not receive an email, it’s often because we do not have a registered account with that email address. Please double-check that you entered the email you provided when you gave your child permission to use Niantic Kids. If you have multiple email addresses, it may help to search your email accounts for the permission email we sent you when your child first created their account.
To reset your child account’s password:
Have your child open their game and attempt to log in using the Niantic Kids login method. Tap the 'Forgot your password" option and follow the prompts to reset their password. An email containing a password reset link will be sent to the parent's email address.