It's actually pretty well predictable if you think about it in terms of encapsulation and core functionality. If this functionality is an external requirement to the purpose of the components, then it absolutely should exist as its own component that coalesces that functionality into a single location. However, if that functionality is core functionality to the components, and they just happen to do the same thing in the same order... Then that's where you'll eventually see divergence if you try to link them to a third component. In those cases, you should either be trying to join the two components into one, or just happily leave them as separate components that just happen to perform some common operations by way of their primary function.