Story-wise they are very distinct, but, if you mean you will find some kind of sense between 47 and other characters in this game that might be true. Not sure if you already completed this one in its entierity so I won't post any spoiler. But Hitman Blood Money is one of the best games to understand this franchise, also the best game in this series in my opinion, Contracts can help too.
But if I play this one without completing any of the other games before it, will the story make sense? Like will I be missing anything important by not finishing the others?shmedo
It's kinda hard to give such details without using at least some spoilers, but suffice it to say this game gives you a brief outline via cutscenes and dialogue of 47's involvement with ICA previous to this installment, as well as how he became an agent, and why he takes the path he pursues in this game. There's not really any reoccurring extraneous villains from past titles, and those he battles in this one are pretty much self explanatory.
The only real reason to play past titles is to get a feel for how the series has evolved, but you won't rreally be missing any details pertinent to this one of you don't. Some of the past titles are definitely worth playing, but if you like using weapons, they were a bit cumbersome in titles past.