first of all im sorry i like them too much i couldn't stop myself so this got a little long… okay so… this is solely my own perspective of their rs… back in iland jw was a self-conscious kid trying to finally break out of his hard shell bc you know…things had gotten really serious in his life. and he's a person who loves making silent sacrifices. he doesn't mind devastating his own life for the people he loves most. i could see why he was the leader the moment he decided to burn the candle of his life by giving up on being in the group (only in words-- he never stopped giving his best) bc he downplayed his talent and thought he wasn't perfect enough, that's when i knew he was someone who would be good for any group he's in. and when sn entered the picture, by picture i mean him coming back from the ground several times like nothing happened, that was the first time he really saw this bright, extroverted kid who never let his soul be crushed, and he probably thought "wow, what a weird kid, so different from me, is he faking? there's no way his soul hasn't fractured yet" and he found him cute. this pale teenager with the face of an angel and with a character that is so loud it leaves an afterimage... he couldn’t stop wanting to know him and to be known by him. maybe he saw sn as his missing broken piece. you know the kind of person you need in your life so that it wouldn't be exhausting being yourself all the time. he knew sn would complete him. so he decided to follow him everywhere he goes, he even decided to tell the world that how he has followed him to get to know him better (that's also one thing i like abt their dynamic, he's so possessive of sn, and as we know he's a very jealous person… that's why i don't rly think anyone is reaching with their jealousy moments. i mean yes he's jealous…especially with sunoo).

anyways, jw wanted to join his orbit but he didn't know sn would find his way into his orbit too. sn saw who he is, that selfless kid with explosive talent and an inspiring personality. he admired him, he was proud of him. when the time came and jungwon threw himself into his arms on the last stage before their debut, he was the happiest person alive. and that hug meant a lot to both of them i think. sn felt his existence accepted by jw without knowing jw was feeling the same way too.

they have this hyung x dongsaeng dynamic which i like a lot. you can catch those little moments where jw looks up to sn even now. (like in that program where it was just the two of them, when they played with the kids and jw wouldn't leave sn's side for a second—THATS HIS HYUNG HE KNOWS HOW TO ACT BEST!!!) he still sees him as his broken piece that would complete him only when attached to him. he knows him as his hyung. and sn knows him as his best friend and he keeps announcing it to the world every chance he gets (he loves mentioning it).

so in short. i think they rly like each other . so much that they keep choosing each other. sn will always give his name and jw will always be the first to step up when he needs him.

hope this answers your question!! their dynamic can be molded into anything but within this frame imo.