how to accomplish:"When click a button , four button occour ."

By unity, I want to get :

When click a button , four buttons occour . So I write codes below :

            public string button1 = "" ;
          
             public string button2 = "" ;    
          
           public string  button3  = "";
              
              void Start()
  `         ` {    
              button1="statement1" ;  
             button2="statement2" ;  
              button3="statement3" ;
               }
              
              void OnGUI()
            `` {  
      `         ` if(GUI.Button(new Rect(60,60,100,30),button1)) 
                      {
      `         `   GUI.Button(new Rect(60,60,100,30),button2) ; 
                    GUI.Button(new Rect(60,60,100,30),button3) ;
           ``      `}
              
                   }
  

when all is ready, and then run this script , the console show some wrong with it. I don't know what's wrong with it and how to accomplish it in unity .