Kevin's dad being on the train is implied from the way he left flowers at the train station and Hedwig said the dad left him at a train station and didn't come back. The only problem with it is Kevin's age doesn't seem to match up, but that could just be an oversight. Knowing Shyamalan and with how blatant these references are, I wouldn't be surprised in the least if he wanted people to connect the Unbreakable train crash with the death of Kevin's father!

The text about young Kevin and his mom being seen in Unbreakable is a bit different 'cause from what I've read, a lot of people disagree on whether or not the mom actress in Unbreakable and situation resembles the one in Split at all, and whether this idea is a reach. And again, there's the age issue.

We do know Shyamalan had planned Kevin's character back with Unbreakable 'cause he's said so. I'm sure as the years have passed, he's made quite a few edits to the character and so we have what we've got now: http://www.latimes.com/entertainment/movies/la-et-mn-split-m-night-shyamalan-20170103-story.html

Yeah, that makes so much sense! I forgot about the flowers.

And thanks so much for the article. I found this quote fascinating:

I believe everything works out when you’re putting your energy into the right place. In the wrong place, the universe slaps you,” he said. “I think, in a literal way, audiences can tell if I’m in a good place, if I’m in a bad place, if I’m in a lost place. You can just tell. You can feel it.

I think I've been slapped by the universe a couple times! And the article somewhat explains the disastrous "The Last Airbender." Cheers