CSHARP

change parent of gameobject in Unity3d

public GameObject Child;
public Transform NewParent;

// Sets "newParent" as the new parent of the child GameObject.
Child.transform.SetParent(NewParent);

// Removes parent, puts child into a top-level object in the hierarchy
Child.transform.SetParent(null);

how to get parent gameobject in unity

childObject.transform.parent.gameObject

set parent of gameobject unity

child.transform.SetParent(newParent);    

how to change a gameobject parent unity

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    public GameObject player;

    //Invoked when a button is pressed.
    public void SetParent(GameObject newParent)
    {
        //Makes the GameObject "newParent" the parent of the GameObject "player".
        player.transform.parent = newParent.transform;

        //Display the parent's name in the console.
        Debug.Log("Player's Parent: " + player.transform.parent.name);

        // Check if the new parent has a parent GameObject.
        if (newParent.transform.parent != null)
        {
            //Display the name of the grand parent of the player.
            Debug.Log("Player's Grand parent: " + player.transform.parent.parent.name);
        }
    }

    public void DetachFromParent()
    {
        // Detaches the transform from its parent.
        transform.parent = null;
    }
}