There Are Many Attempts at Backstory, and None of Them Stick
First of all, every supporting character got a special still in the promotional images, from Christian's entire family to Anastasia's photographer friend who's so insignificant, his name escapes me. And that's kind of the point. None of these characters pull a huge weight in the film, except maybe Anastasia's roommate. Christian's family and Anastasia's family both get a couple measly scenes each, during which we find out little to nothing about them.
Why does Christian's mom stop by for less than a minute, then leave? Why don't we see more of Christian's brother and Anastasia's roommate (again, I forget their names)? If you're going to highlight side characters, at least flesh them out a little, right?