If you need to, you can have the same objects in different families. I do that with my game, but you will need to be clear with your code as it might overlap sometimes, but it can prove very useful.
You can select an object inside a family just by its UID. You need to save it to a global, and as you mention pick it using the global. If you are having issues with selecting the UID, you can share a capx here and we will be able to help you out.