グループのユーザーを追加したら、他のグループにもユーザーが追加されている

Question

グループ機能を制作しているのですが、グループにユーザーを追加すると他のグループにもユーザーが追加されてしまいます。
初学者なのでわかりやすく教えていただきたいです。

circle.controller


class CirclesController < ApplicationController
   before_action :set_circle, only: [:update, :destroy, :edit]
   before_action :set_parents, only: [:new, :create, :destroy]
   before_action :owner_user,     only: [:edit, :destroy]
   
  def index
    @circles = Circle.paginate(page: params[:page]).search(params[:search])
  end
  
  def member 
    @members = CircleUser.paginate(page: params[:page])
  end
  
  def new
    @circle = Circle.new
  end
  
  def show
    @circle = Circle.find(params[:id])
    @circleposts = @circle.circleposts.paginate(page: params[:page])
    @circleposts = Circlepost.where(circle_id: @circle.id).all
  end

  def create
    @circle = Circle.new(circle_params)
    @circle.owner = current_user
    if @circle.save
      @circle_user = @circle.owner
      flash[:success] = "作成しました"
      redirect_to root_url
    else
      render :new
    end
  end
  
  def edit
     @circle = Circle.find(params[:id])
  end
  
  def update
    @circle = Circle.find(params[:id])
    if @circle.update(circle_params)
      flash[:success] = "サークル情報が更新されました"
      redirect_to @circle
    else
      render 'edit'
    end
  end
 
  def destroy
    @circle = Circle.find_by(id: params[:id])
  return redirect_to :root if @circle.nil?
    @circle.destroy
    flash[:success] = 'サークルを削除しました。'
    redirect_to :root
  end

  def search
    if params[:name].present?
      @circles = Circle.where('name LIKE ?', "%#{params[:name]}%")
    else
      @circles = Circle.none
    end
  end
  
  def set_parents
    @parents = Category.where(ancestry: nil)
  end
  
  def get_category_children
    @category_children = Category.find("#{params[:parent_id]}").children
  end
  
  def get_category_grandchildren
    @category_grandchildren = Category.find("#{params[:child_id]}").children
  end
  
  def top
    respond_to do |format|
      format.html
      format.json do
        if params[:parent_id]
          @childrens = Category.find(params[:parent_id]).children
        elsif params[:children_id]
          @grandChilds = Category.find(params[:children_id]).children
        elsif params[:gcchildren_id]
          @parents = Category.where(id: params[:gcchildren_id])
        end
      end
    end
  end
  
  private
  
  def owner_user
      redirect_to(root_url) unless current_user && @circle.owner?
  end
  
  def circle_params
    params.require(:circle).permit(:categries_id, :category_grandchildren, :category_children, :parent_id, :name, :place, :time, :homepage, :profile, { :user_ids => [] })
  end
  
  def set_circle
    @circle = Circle.find(params[:id])
  end
  
end

circle_user.controller

class CircleUsersController < ApplicationController
  
  def index
   @circles = current_user.circles.paginate(page: params[:page])
  end
  
  def create
        @circle_user = CircleUser.create(circle_id: circle_user_params[:circle_id], user_id: circle_user_params[:user_id])
        Apply.find(circle_user_params[:apply_id]).destroy!
        redirect_to circle_applies_url(@circle_user.circle)
        # @circle.user = current_user
        flash[:success] = "「#{@circle_user.user.name}」が、サークル「#{@circle_user.circle.name}」へ加入しました。"
  end
 
  def destroy
        @circle_user = CircleUser.find(params[:id])
        @circle.user.destroy!
        @circle = Circle.find(params[:circle_id])
        redirect_to circle_url(@circle), notice: "サークル「#{@circle.name}」を退会しました。"    
  end
  
  def show 
    @circle_user = CircleUser.find(params[:id])
  end
  
  private

    def circle_user_params
      params.permit(:circle_id, :user_id, :apply_id)
    end
    
end