Drag the children of an empty game object in 2d, correctly

For my current project, I have a series of polyominoes (like the pieces of tetris) that are formed that some squares that are linked together by being parented to an empty game object. I need to drag each piece with the mouse. With my current code, I notice that wherever I click in the piece, the mouse pointer is always on top of the piece. What should I change in my code so that when I click, the mouse pointer keeps being on the same point of the piece?

//This is the script attached to the squares

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class SquareClickChild : MonoBehaviour {
     
     public void OnMouseDown()
     {
         gameObject.transform.parent.GetComponent<SquareClick>().ParentOnMouseDown();
     }
 
     public void OnMouseUp()
     {
         gameObject.transform.parent.GetComponent<SquareClick>().ParentOnMouseUp();
     }
 
 }
 
   

//This is the script attached to their parent, the empty game object using System.Collections; using System.Collections.Generic; using UnityEngine;

 public class SquareClick : MonoBehaviour {
 
     private Vector3 OriginalPosition;
     private float Scale = 3.3f;
     private bool dragging;
     private float distance;
 
     private void Start()
     {
         OriginalPosition = gameObject.transform.localPosition;
         dragging = false;
     }
 
     public void ParentOnMouseDown()
     {
         gameObject.transform.localScale = new Vector3(Scale, Scale, gameObject.transform.localScale.z);
         distance = Vector3.Distance(transform.position, Camera.main.transform.position);
         dragging = true;
     }
 
     public void Update()
     {
         if (dragging)
         {
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             Vector3 rayPoint = ray.GetPoint(distance);
             transform.position = rayPoint;
         }
     }
 
     public void ParentOnMouseUp()
     {
         //The piece goes back to its original position, it works well so I won't post it here;
     }
 
 }