Parent rigidbody using its childrens colliders. Should it work or am I stupid?

Hey there..

I'm working on a little something and I ran into this (to me) weird issue. As I have read on countless websites and even here on unity answers, when you make an empty gameObject, give it a rigidbody (without any colliders) and then, as it's children, you put let's say a bunch of cubes (with colliders) the parent rigidbody should use those colliders as it's own, thus having no problems colliding with the environment. The parent in my project doesn't seem to be using it's childrens colliders... It just goes right trough everything...

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I find this more 'realisticly' looking than just swaping the whole object for the 'broken' prefab. As you can break it down piece by piece.

Unfortunately, this is only working for static objects such as the walls, and that is why I am trying to get the parent rigidbody to use it's childrens colliders. So I could make these objects breakable and moveable at the same time. Ofcourse, I could always ust use the 'object swapping', but as I've said, this looks better IMO.

Here's a video if anyone's interested. YouTube Link