Harry and Zayn were the only ones in the band who like reading and art so I feel that may have forged an initial bond. They seemed close in 2013. Louis and Niall are similar- laddy, like beer and sport, both extroverts who like going out to pubs and bars. Liam is another extrovert who's more into fitness than Niam and tends not to be as laddy. I can see why Zayn and Harry felt out of place in 1d.
Well that’s a different take for today! I’m not sure what “laddy” means, exactly, but whatever drew certain members together or apart, it’s well and truly deceased at the moment. RIP, 1D.