In the movie Split there is a scene where James McAvoy's character is buying flowers. He leaves the flowers on the floor and gets on the train. Which personality is this guy? Why does he buy the flowers and who does he leave the flowers on the floor of the station for?
Kevin told of how he never saw his father again after he left from a train station.
Kevin, using Dennis's personality, goes into 30th Street Station to buy flowers before The Beast comes. He lies the flowers down on the Amtrak platform in reverence before going into a train and turns into The Beast.
Dennis bought the flowers for his dead father, who was supposed to arrive at the platform to return to his family.
So it seems the death of his father could also have some influence over the birth of his multiple personalities.
Without a father, Kevin had no one to prevent his mother from beating him, which later led to the creation of The Beast.