Add instantiated class to gameobject

I am creating 10 cubes over runtime and I need to add an object which is not inherited from Mono Behaviour. I have looked at Add Component but that needs a class to be inherited Mono Behaviour. So is there any other option.

So here is the scenario:

I am creating a cube at random positions and I need to save that initial position attached to the Cube gameObject so I can access it as and when needed. So what is the possible option.

Looking for a vector3 to be attached to a gameObject?

Why not monobehaviour?

using UnityEngine;
using System.Collections;

public class PositionGrabber : MonoBehaviour {
     public Vector3 initialPosition;

     void Start() {
         initialPosition = transform.position;