Password reset for Apple Account that doesnt exist

It's possibly and likely a scam.

But it's usual for Apple to send emails for login attempts to Apple Accounts to the rescue email on file.

However, the usage of your name with his email is very strange. Even when sending these emails, Apple will us the name on file for the account that was attempted to be logged into, not some other name for no discernible reason.

If you are 100% sure your grand father's email accounts has not been used as the primary email address for an Apple Account, then this pretty surely a scam and can be ignored.

Does it have a link to somewhere to "reset" the password? If so, that's a dead giveaway, Apple won't add a reset link. They will instruct you to do so on your device.

You can forward it to Apple at reportphishing@apple.com

click here ➜ Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

The links are correct.

It is possible his email address was used to create an Apple Account with your email address as a rescue email in that case.

If he has any Apple device, like an iPad, an Apple TV, or just uses Apple services on other devices like an Android phone or Smart Tv, then its possibly he made an Apple account with his email address and your name, though its kind of odd.

Where on your laptop did you try to log on to the account? His email provider's website? Or an Apple website?

Or in settings on your laptop?

If the Apple website says the account is locked, then it exists and is locked.

Which means his email address is in fact associated with an Apple Account.

In which case, you can go to iForgot and try to reset it to gain access to it.