How Can I Stop My Photos from Syncing to My Dad’s Google Account?

Honestly, the easiest fix is to just remove his account from your phone and start fresh with your own Google account. There’s no need for a factory reset unless nothing else solves the issue. When it's set up correctly, your phone will operate independently of his account, so you can keep your stuff private without any worries.

It sounds like your dad's Google account was the one used when setting up your phone. I suggest logging out of his account and then signing in with your own Google account. This way, you can keep your photos separate. Just remember, account billing is usually handled through the telecom service provider, so removing his account shouldn't affect how the phone bill is paid. Also, if you're worried, you can share certain services with each other through Google Family sharing without being logged into the same account.

If you're using an Android phone, it's pretty likely that your dad's account was set up as the main one, which is what causes this syncing issue. You should definitely log out of his account and create your own. You can also check if you're set up to share photos—if you are, that's why they're ending up in his account. Just make sure to take a test photo after signing in with your account to verify that it's no longer syncing to his Google Photos.