An error for displayobject--r

I want to create a two buttons for single function and click the same object to make it dissappear in my web. For example, i click "A" and "B", the screen will show "C"object. If I click "C", C will dissappear. I try to make this by removeChild, but it occurs an error when I click "A" and "B" twice

ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.

          at flash.display::DisplayObjectContainer/removeChild()

          at Function/Page2MC/bothClickedF/page1Click()[Page2MC::frame1:82]

import flash.display.MovieClip;

import flash.events.MouseEvent;

import flash.events.Event;

import flash.ui.Mouse;

var redbtn:MovieClip=new Redbtn();

redbtn.x=321;

redbtn.y=13;

addChild(redbtn);

var bluebtn:MovieClip=new Bluebtn();

bluebtn.x=726;

bluebtn.y=89;

addChild(bluebtn);

var page1:MovieClip=new relationship();

var redBtnClicked:Boolean;

var blueBtnClicked:Boolean;

redbtn.addEventListener(MouseEvent.CLICK, onRedBtnClick);

redbtn.addEventListener(MouseEvent.ROLL_OVER, onRedOver);

redbtn.addEventListener(MouseEvent.ROLL_OUT, onRedOut);

bluebtn.addEventListener(MouseEvent.CLICK, onBlueClick);

bluebtn.addEventListener(MouseEvent.MOUSE_OVER, onBlueOver);

function onRedOver(evt:MouseEvent):void{

          redbtn.gotoAndStop(2);

}

function onRedOut(evt:MouseEvent):void{

          redbtn.gotoAndStop(3);

}

function onBlueOver(evt:MouseEvent):void{

          trace("blueover");

}

function onRedBtnClick(evt:MouseEvent):void{

          redBtnClicked=true;

          bothClickedF();

}

function onBlueClick(evt:MouseEvent):void{

          blueBtnClicked=true;

          bothClickedF();

}

function bothClickedF():void{

          if (blueBtnClicked&& redBtnClicked){

                    trace("two buttons are clicked");

                    addChild(page1);

                    redBtnClicked=false;

                    blueBtnClicked=false;

                    page1.circleC.addEventListener(MouseEvent.CLICK, page1Click);

function page1Click(evt:MouseEvent):void{

   removeChild(page1);

}

                    }