We regularly verify the legitimacy of the YouTube accounts. This is part of a process to ensure that our site metrics are free of spam and abuse and to keep YouTube a fair playing field for everyone.
You need to sign in to your accounts to take it down. You'll need to have at least one of your account related information (i.e email / username and any recovery options, if set up). Once you have that here's how you can regain access: https://goo.gl/v7CdWx . Hope this helps!