public class MyGroup extends Group {

  ...

  MyActor child = new MyActor();
  addActor(child);

  ...

myListener = new ClickListener() {

  public void clicked(InputEvent event, float x, float y) {

    Actor target = event.getTarget();
    MyGroup group;

    if (target instanceof MyActor){
      group = (MyGroup)target.getParent();
    } else {
      group = (MyGroup)target;
    }

    // manage event and change the state of "group"...

  }
};