Harry Styles has always been that odd ball out when it came to taking care of people. While all of his friends were out getting drunk and fucking people just for the fun of it, he was out working at the bakery with the old ladies who, he thought, were just as funny as can be. He was a natural born caregiver and a definite old soul.
Louis Tomlinson has always been that one person who just couldn't take care of someone if his life depended on it. He would rather people be taking care of him than him taking care of people. He would rather stay in his apartment watching Disney movies than go out with his friends and get drunk most of the time. Lucky for him, though, he's got two friends - Eleanor and Liam - to take care of him.
(I am shit at writing descriptions, but I hope this tells you a bit about the story without giving the whole story away.)