Sprites that moves overlapping

Hi, I'm currently working on a project in which some NPCs are spawned in the scene. These NPCs are represented by Sprites and they move 'walk in a street', moving from one point to another. Their start and end positions are generated randomly:

 using UnityEngine;
 using System.Collections;
 
 public class ClientSpawner : MonoBehaviour
 {
     [SerializeField]
     private float _spawnTime; 
 
     [SerializeField]
     private GameObject[] _clientCharacter;
 
     [SerializeField]
     private int _clientCount;
 
     [SerializeField]
     private Transform _gameArea;
 
     [SerializeField]
     private float _padding;
 
     private int _clientsSpawned = 0;
 
     private Vector4 _bounds;
     
     private void Start()
     {
         Vector3 min = Camera.main.ScreenToWorldPoint( UICamera.mainCamera.WorldToScreenPoint( _gameArea.collider.bounds.min ) );
         Vector3 max = Camera.main.ScreenToWorldPoint( UICamera.mainCamera.WorldToScreenPoint( _gameArea.collider.bounds.max ) );
 
         _bounds = new Vector4( min.x + _padding,
                                max.x - _padding,
                                min.z + _padding,
                                max.z - _padding );
 
         if ( _clientCount > 0 )
             InvokeRepeating ("Spawn", 0, _spawnTime);
     }
 
     private Vector3 SortPosition( bool atRight )
     {
         Vector3 position;
         if ( atRight )
             position =  new Vector3( _bounds[0], 0f, Random.Range( _bounds[2], _bounds[3] ) );
         else 
             position =  new Vector3( _bounds[1], 0f, Random.Range( _bounds[2], _bounds[3] ) );
 
         return position;
     }
 
     private void Spawn()
     {
         _clientsSpawned ++;
 
         if(_clientsSpawned == _clientCount)
             CancelInvoke( "Spawn" );
 
         bool atRight = ( Random.Range(0, 2) == 1 );
 
         Vector3 startPosition = SortPosition( atRight );
         Vector3 finalPosition = SortPosition( !atRight );
          
         GameObject client = GameObject.Instantiate( _clientCharacter[Random.Range( 0, _clientCharacter.Length )], 
                                                    startPosition, Quaternion.identity ) as GameObject;
 
         if (!atRight)
         {
             Flip( client.GetComponentInChildren<Transform>() );
         }
 
         client.GetComponent<ClientBehavior>().EndPosition = finalPosition;
         client.SetActive( true );
         client.transform.parent = transform;
     }
 
     private void Flip( Transform t )
     {
         Vector3 scale = t.localScale;
         scale.x *= -1;
         t.localScale = scale;
     }
 }

When they are walking, they may pass through a common position. In this case, however, I have no control of which NPC will be in front of the other, getting some incorrect cases:

How could I correctly treat this? My NPCs have a script in which they only know what should be their final positions:

 public class ClientBehavior : MonoBehaviour
 {
     private Animator _animator;
 
     private int _state; /** 0 (idle), 1 (walking) or 2 (restless) **/
 
     [SerializeField]
     private float _velocity;
 
     private Vector3 _endPosition = Vector3.zero;
     public Vector3 EndPosition
     { 
         get { return _endPosition; }
         set { _endPosition = value; }
     }
 
     private void Awake()
     {
         _controller = GetComponent<CharacterController>();
         _animator = GetComponentInChildren<Animator>();
 
         _state = 1;
         _animator.SetInteger("State", _state);
     }
     
     private void FixedUpdate()
     {
         if ( _state == 1 )
             Walk();
     }
 
     private void Walk()
     {
         transform.position = Vector3.MoveTowards(transform.position, _endPosition, _velocity * Time.fixedDeltaTime);
 
 //        Vector3 dir = ( _endPosition - transform.position ).normalized;
 //        dir *= _velocity * Time.fixedDeltaTime;
 //        _controller.SimpleMove( dir );
     }
 }
 

Thank you.