Make Child face direction of analog RELATIVE to parent's direction

As the titles suggests, how do I make a child object face the direction of the analog stick I'm pressing relative to the parent's position?

Here is my code

var dir = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));

     var rDir = new Vector3(Input.GetAxis("Horizontal2"), 0, 0);

     //Vector3 test = transform.TransformPoint(dir);


     //print ("test: " + test);

     if(rDir.x != 0)
     {
         transform.Rotate(Vector3.up * rDir.x * cmv.rotateSpeed * Time.deltaTime);
     }

     else
     {
         transform.Rotate(Vector3.up * 0);
     }

     if(cmv.moveDirection.x == 0 && cmv.moveDirection.z == 0)
     {
         mv.model.transform.forward = transform.forward;
     }

     else if (cmv.moveDirection != Vector3.zero)
     {
         mv.model.transform.forward = Vector3.Normalize(dir);
     }

I rotate with the right analog stick and that's what the Horizontal2 is, that works fine and the child faces the direction of the parent object while rotating.

When I tell the child object to face dir, that dir gets a Vector3 based on the input of the left analog stick. The problem is that this Vector3 is relative to the world space. How do I convert this Vector3 from world space relativity to local relativity?