Long Story really, but, I had a '17 sonata, my BIL has a15 Fusion EB. The structure and certain points of both cars are identical, not close, but Exactly the same. I posted a thread about it,
http://www.therangerstation.com/forums/index.php?threads/hyundai-got-me-thinking.179127/, and I also notice Hyundai/Kia had a 3.8L v6, a 5.0L V8, they used to run a 4.6L v8 until recently. Ford helped Hyundai back in the 60's break into the car industry, and have shared a few other cars since then. All of this plus the fact that Ford dumped Mazda, then a few years later Hyundai/Kia becomes a more reputable brand with styling a LOT like fords. I think if you strip the car down to sheet metal, you would see that they are identical.
Little things are different, like the Fusions rearview mirror was on the Door and the Sonatas was in the window.
The interiors are very similar as well. but what really convinced me was when we had the 2 cars side by side, the Hoods, trunks, and doors, all had the same hardware and were IDENTICAL at the hinges and latch points.
EDIT: to me, it's not that fart fetched, I mean in the 90's, you had the Cougar and Thunderbird, essentially the same car, but very different styles.