Is This Why Jennifer Aniston & Justin Theroux Broke Up?

Jennifer Aniston and Justin Theroux's split seemed to come out of nowhere, but if you believe some, the couple was doomed from the start.
One source told People the actors were just always "very different people."
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That certainly always felt true, but that's what made the couple great; they were complementary.
But another source says there was a more specific difference we didn't see when they were together - because it was all about them being