Do you think there was something more than friendship between Jonghyun and Kibum? I mean not like an official love story but you know... something in the gray zone?
I mean i noticed (and i think many other people did notice too) that Kibum literally made heart eyes at Jonghyun everytime he was close to him. I guess many times it was fanservice, but i don't know there's something very special about these two and it's not even a defined thing. Like i said before, something gray. They fascinate me so much...
Okay, I'm really not the best person to give you a satisfying or comprehensive answer to this, because my view on Junkey and 2men has been skewed forever by the toxic fans that were shipping these ships back then and using it as an excuse to misrepresent or reduce members to perceptions that fit their narrative.
That being said. If I go back to pre-2013, I would say that they definitely were the closest. (From 2013 and afterwards, I noticed Jongkey were less tightly-knit, giving way to lots of Minkey and Jongyu interactions).
I think Key mentioned how Jonghyun would always back him when no one else would and make him feel more confident in himself back then.
And in general, I definitely believe that Jonghyun was the glue in the group, meaning that he had a special bond with each and everyone one of them. I think the more you watch their dynamics, the more you can see everyone was actually making heart eyes at Jjong.
I do believe Key in particular put Jjong on a pedestal (a little akin to how Taem does but the dynamics aren't exactly the same, because Tae was the youngest) and when I actually can remove my biased goggles, I can't deny they had something special. Now was it anything more than friendship... I think if it was, it was more of a one-sided thing (like Key crushing on him). I think there was a reason when Jjong was asked who he would choose to go out with in the members, he picked Jinki (and he said it two times btw - once written).
I think Jonghyun meant that as this is someone I can rely on without it interfering with my sense of responsibility towards them. I think because Jinki was the oldest, he gave off that sense of security/reassurance that Jonghyun was looking for at times. Not saying he was in love with Jinki either, just saying I don't think Key would be his kind of partner, but that's just my impression/opinion.
To end, I would say that as much as some things could be fanservice, there is no denying that the deep bond between Jonghyun and Key was very real. And that is true for all of them. Like they have a love for each other that you really don't see in other groups.