Lonely
It's Christmas, and Peter is sitting in his living room listening to the Beatles on the record player his parents left under the tree for him—the only outward display of affection he's seen from them since he's been home.
"All the lonely people, where do they all come from?"
After six years of wondering the very same question, Peter thinks he has an answer for the famous foursome. They come from overbearing mothers and absent fathers in museum houses where children are to be seen, not heard. They come from being homeschooled until their Hogwarts letter comes on their eleventh birthday to rescue them from their mothers' harsh reproofs. They come from being a member of another sort of famous foursome by proxy rather than voluntary inclusion by the other three.
"All the lonely people, where do they all belong?"
Peter hasn't quite worked out an answer to this one, but as he stares at the fire and rubs at an imaginary itch on his left forearm, he thinks he has an idea.