Think it's okay to talk to my friends parent without him knowing?
Why would you talk to your friends parents without your friend knowing?
Because my friend will be mad at me
You are being sneaky by going behind your friends back to speak to his parents. If you cannot be honest with your friend then you o not deserve to have him as a friend.
Fuck it. But what if he is going to talk bad about me behind my back too?
Sounds like there needs to be a lot more communication between you two. How would he feel if you kept going behind his back like this? Why not just ask him what's going on and be more honest to yourself and him?