Collider/Rigidbody not working as expected

Disclaimer: Am a noob. But from what I understand about collisions, both objects must have colliders and one must have a Rigidbody. I currently have a Rigidbody and Sphere collider on my player, and a collider on the obstacle game object.

Player:

Other Object:

And the Destroy script on my obstacle object is as follows:

 using System.Collections;  
 using System.Collections.Generic;  
 using UnityEngine;  
 
 public class Destroy : MonoBehaviour  
 
 {  
 
 void OnTriggerEnter(Collider col)   
     {  
     Destroy(col.gameObject);  
     }  
 }  

My player is currently passing through the object and the collision is going undetected.

I should also mention that the obstacle object is a grand-child object, and both parents have neither rigid bodies nor colliders on them (I believe this is where I am running into trouble). Thank you very much for any help/advice anyone can give!