Problem detecting collision without rigidbody

Hi there!
I’m trying to make this game where I have some circle colliders without rigidbody. I have 2 empty game objects, each object has the same script attached. For each empty game objects I have 6 child circle sprites, each with a circle collider around it. The 6 circles in the parent empty game object rotate around a center, and they all have the same distance between each other, making a hexagon. Each circle has a script attached (the same script), which is the following:
using UnityEngine;
using System.Collections;

public class CircleDestroyer : MonoBehaviour {

	void Update () {


	void OnTriggerEnter2D (Collider2D any) {

		Debug.Log ("Overlap!");



For some reason when the circles from different parents aren’t detecting collision.
Can you help me?

In order to detect trigger collisions between two objects, make sure the following is true:

  1. at least one of them has a collider with “isTrigger” set to true.
  2. at least one of them has a rigidbody
  3. both are on layers that detect each other in physics settings.
  4. your detecting script is on the desired object(s)

Remember also to consult the collision docs for details of what combination of things will send and receive collision messages.