One of the attributes of a container is that it creates everything in the container if one thing in it is created.
Same goes for when one part is destroyed.
Found out an interesting bit of information tonight myself. That being that the other parts of the container are created at their resting place on the editor, even if the one part that was created was "spawned".
......runs off to play with the Object Pairer.
Might want to check that one out yourself.