Mia's parents are the friends-first type, liberals who don't mind if their daughter takes a boy to her room with the door closed. They take their daughter to Planned Parenthood for birth control. Dad smokes a pipe, and Mia isn't sure if his affectation is "sartorial or sardonic" (1.4). Translation: she doesn't know if he's doing it because he likes the look, or if he's doing it because he's a hipster mocking the look.
Both parents are aging hipster types. Mom was a former rock chick, and Dad was in a band, but both have given it up to raise children. Mia tells us that Mom is a protector, even in death. "She was the one to buffer us from the blow" (3.7), Mia says, because the accident happened on the passenger side. Well, she did a terrible job, because most of the family died, anyway.
Finally, Teddy is the classical lovable brother type, complete with cuddly name. He is perfect, like Mia and her family. He is more like a son to Mia than a brother due to the big age difference. He isn't even annoying, as little brothers generally are.
We're told over and over by Adam and Mia that Mia's "parents are so cool" (4.46). What makes them cool? Their friendly attitudes? The way they support each other? Their trendy clothes? Or something else?