constructor TComponent.Create(AOwner: TComponent);
begin
  FComponentStyle := [csInheritable];
  if AOwner <> nil then AOwner.InsertComponent(Self);//将自己插入到所属者的所属列表中，方便所属者destroy时把自己释放
end;

destructor TComponent.Destroy;
begin
  Destroying;
  RemoveFreeNotifications;
  DestroyComponents; //释放
  if FOwner <> nil then FOwner.RemoveComponent(Self);
  FObservers.Free;
  inherited Destro
end;
procedure TComponent.DestroyComponents;
var
  Instance: TComponent;
begin
  FreeAndNil(FSortedComponents);
  while FComponents <> nil do //循环释放自己下面所有的Tcomponent
  begin
    Instance := FComponents.Last;
    if (csFreeNotification in Instance.FComponentState)
      or (FComponentState * [csDesigning, csInline] = [csDesigning, csInline]) then
      RemoveComponent(Instance)
    else
      Remove(Instance);
    Instance.Destroy;
  end;
end;

TMyClassA=class(TButton)
  public
    procedure KKK(); virtual;
  end;
  TMyClassB=class(TMyClassA)
  public
    procedure KKK();override;
  end;
  TMyClassC=class(TMyClassB)
  public
    procedure KKK(); override;
  end
  
procedure TForm1.FormCreate(Sender: TObject);
begin
    A:=TMyClassA.Create(nil);
    B:=TMyClassB.Create(nil);
    C:=TMyClassC.Create(nil);
    B.InsertComponent(TComponent(A));  //释放B时会连带释放A；以为A已经放到了B里面去管理了
end;