How can i rotate a object more than once (90 degrees)?

Hey, maybe someone can help. I want two separate Sprite-Objects to rotate after clicking +90 degrees. So that they rotate first from 0 to 90, than from 90 to 180, than from 180 to 270 and finally from 270 to 360/0. But not the Sprite-Object itself should rotate. They should linked to an Layer-Object, that rotates. All of them, Layer-Object and Sprite-Objects, should rotate together and not on each own pivot point. So if i click on one Sprite-Object it becomes a c$$anonymous$$ld of the Layer-Object. After i clicked on the other Sprite-Object it also becomes a c$$anonymous$$ld of the Layer-Object, too.

Code for the Sprites:

     public GameObject Layer1;
 public GameObject Layer2;
 public GameObject Brick;

 void Start () {

 }

 // if you click the Brick it becoming c$$anonymous$$ld of Layer
  void OnMouseDown (){
     if (Brick){
             Brick.transform.parent = Layer1.transform;
         }                 
         print ("Brick is clicked");
     } 

Ok, now they are both clicked and linked to the Layer. In the next step i check the numbers of c$$anonymous$$ldren in the Layer-Object. If the Layer-Object has two c$$anonymous$$ldren, it rotates from 0 to 90. That works. After t$$anonymous$$s step, i want all c$$anonymous$$ldren to be unlinked and send back to the normal Brick-Folder, where they belong. So that the Layer-Object is empty again. That works, too. But the next step doesn't work: I want to click again on each Sprite-Object, so that the rotation repeats. Finally it should be as follows: i want to click on two Sprite-Objects. They become c$$anonymous$$ldren of the Layer-Object. The Layer-Object rotates with both c$$anonymous$$ldren inside. After the rotation from 0 to 90 is completed, the Layer-Object should become "empty" again. T$$anonymous$$s should be round one! If i repeat the click on the two Sprite-Objects, i want the next rotation of the Layer-Object from 90 to 180. And so on and on... Maybe someone can help.

Thanks and best Greetings. Simon

Code for the Layer:

 public GameObject Bricks;
 float t;
 Quaternion initial = Quaternion.Euler (0,0,0) ;
 Quaternion target = Quaternion.Euler (0,0,90) ;


 void Start () {

 }

 void Update () {
     print ("Number of C$$anonymous$$lds: "+transform.c$$anonymous$$ldCount);
     Rotate ();
     Unc$$anonymous$$ld ();
 }
     
 public void Rotate () {
     // if the Layer has two C$$anonymous$$ldren -> rotate
     if (transform.c$$anonymous$$ldCount == 2) {
         t += Time.deltaTime; 
         transform.rotation = Quaternion.Lerp(initial, target, t);  // <---------- how can i code that dynamic? that it goes automatic +90?
         print ("rotate");
     }    
 }
     
 public void Unc$$anonymous$$ld () {
     // c$$anonymous$$ld should go in Bricks, after rotation
     if (t$$anonymous$$s.transform.rotation.eulerAngles.z == 90) {    // <---------- i want here somet$$anonymous$$ng like, if the new rotation is done
         foreach (Transform c$$anonymous$$ld in transform) {
             c$$anonymous$$ld.transform.parent = Bricks.transform;
             print ("C$$anonymous$$ld is back in Bricks");
         }
     }
 }