Collision between CharacterControllers

I have two characters both have CharacterController and Rigidbody(isKinematic uncheck).

When moving around the collision work fine, but OnCollisionEnter() Doesn’t called when collision happened. Howerver, OncollisionEnter() do called when the character is hit by a Bullet, which has BoxCollider and Rigidbody.

Is this situation normal or there may be a bug in my script?

You might want to take a look at that :